diff --git a/archivebox/machine/tests/__init__.py b/archivebox/machine/tests/__init__.py
new file mode 100644
index 00000000..d7ce160b
--- /dev/null
+++ b/archivebox/machine/tests/__init__.py
@@ -0,0 +1 @@
+"""Tests for the machine module (Machine, NetworkInterface, Binary, Process models)."""
diff --git a/archivebox/machine/tests/test_machine_models.py b/archivebox/machine/tests/test_machine_models.py
new file mode 100644
index 00000000..bfbe2968
--- /dev/null
+++ b/archivebox/machine/tests/test_machine_models.py
@@ -0,0 +1,474 @@
+"""
+Unit tests for machine module models: Machine, NetworkInterface, Binary, Process.
+
+Tests cover:
+1. Machine model creation and current() method
+2. NetworkInterface model and network detection
+3. Binary model lifecycle and state machine
+4. Process model lifecycle and state machine
+5. JSONL serialization/deserialization
+6. Manager methods
+"""
+
+import os
+import tempfile
+from pathlib import Path
+from datetime import timedelta
+
+import pytest
+from django.test import TestCase, override_settings
+from django.utils import timezone
+
+from archivebox.machine.models import (
+    Machine,
+    NetworkInterface,
+    Binary,
+    Process,
+    BinaryMachine,
+    ProcessMachine,
+    MACHINE_RECHECK_INTERVAL,
+    NETWORK_INTERFACE_RECHECK_INTERVAL,
+    BINARY_RECHECK_INTERVAL,
+    _CURRENT_MACHINE,
+    _CURRENT_INTERFACE,
+    _CURRENT_BINARIES,
+)
+
+
+class TestMachineModel(TestCase):
+    """Test the Machine model."""
+
+    def setUp(self):
+        """Reset cached machine between tests."""
+        import archivebox.machine.models as models
+        models._CURRENT_MACHINE = None
+
+    def test_machine_current_creates_machine(self):
+        """Machine.current() should create a machine if none exists."""
+        machine = Machine.current()
+
+        self.assertIsNotNone(machine)
+        self.assertIsNotNone(machine.id)
+        self.assertIsNotNone(machine.guid)
+        self.assertEqual(machine.hostname, os.uname().nodename)
+        self.assertIn(machine.os_family, ['linux', 'darwin', 'windows', 'freebsd'])
+
+    def test_machine_current_returns_cached(self):
+        """Machine.current() should return cached machine within recheck interval."""
+        machine1 = Machine.current()
+        machine2 = Machine.current()
+
+        self.assertEqual(machine1.id, machine2.id)
+
+    def test_machine_current_refreshes_after_interval(self):
+        """Machine.current() should refresh after recheck interval."""
+        import archivebox.machine.models as models
+
+        machine1 = Machine.current()
+
+        # Manually expire the cache by modifying modified_at
+        machine1.modified_at = timezone.now() - timedelta(seconds=MACHINE_RECHECK_INTERVAL + 1)
+        machine1.save()
+        models._CURRENT_MACHINE = machine1
+
+        machine2 = Machine.current()
+
+        # Should have fetched/updated the machine (same GUID)
+        self.assertEqual(machine1.guid, machine2.guid)
+
+    def test_machine_to_json(self):
+        """Machine.to_json() should serialize correctly."""
+        machine = Machine.current()
+        json_data = machine.to_json()
+
+        self.assertEqual(json_data['type'], 'Machine')
+        self.assertEqual(json_data['id'], str(machine.id))
+        self.assertEqual(json_data['guid'], machine.guid)
+        self.assertEqual(json_data['hostname'], machine.hostname)
+        self.assertIn('os_arch', json_data)
+        self.assertIn('os_family', json_data)
+
+    def test_machine_to_jsonl(self):
+        """Machine.to_jsonl() should yield JSON records."""
+        machine = Machine.current()
+        records = list(machine.to_jsonl())
+
+        self.assertEqual(len(records), 1)
+        self.assertEqual(records[0]['type'], 'Machine')
+        self.assertEqual(records[0]['id'], str(machine.id))
+
+    def test_machine_to_jsonl_deduplication(self):
+        """Machine.to_jsonl() should deduplicate with seen set."""
+        machine = Machine.current()
+        seen = set()
+
+        records1 = list(machine.to_jsonl(seen=seen))
+        records2 = list(machine.to_jsonl(seen=seen))
+
+        self.assertEqual(len(records1), 1)
+        self.assertEqual(len(records2), 0)  # Already seen
+
+    def test_machine_from_json_update(self):
+        """Machine.from_json() should update machine config."""
+        machine = Machine.current()
+        record = {
+            '_method': 'update',
+            'key': 'WGET_BINARY',
+            'value': '/usr/bin/wget',
+        }
+
+        result = Machine.from_json(record)
+
+        self.assertIsNotNone(result)
+        self.assertEqual(result.config.get('WGET_BINARY'), '/usr/bin/wget')
+
+    def test_machine_from_json_invalid(self):
+        """Machine.from_json() should return None for invalid records."""
+        result = Machine.from_json({'invalid': 'record'})
+        self.assertIsNone(result)
+
+    def test_machine_manager_current(self):
+        """Machine.objects.current() should return current machine."""
+        machine = Machine.objects.current()
+        self.assertIsNotNone(machine)
+        self.assertEqual(machine.id, Machine.current().id)
+
+
+class TestNetworkInterfaceModel(TestCase):
+    """Test the NetworkInterface model."""
+
+    def setUp(self):
+        """Reset cached interface between tests."""
+        import archivebox.machine.models as models
+        models._CURRENT_MACHINE = None
+        models._CURRENT_INTERFACE = None
+
+    def test_networkinterface_current_creates_interface(self):
+        """NetworkInterface.current() should create an interface if none exists."""
+        interface = NetworkInterface.current()
+
+        self.assertIsNotNone(interface)
+        self.assertIsNotNone(interface.id)
+        self.assertIsNotNone(interface.machine)
+        # IP addresses should be populated
+        self.assertIsNotNone(interface.ip_local)
+
+    def test_networkinterface_current_returns_cached(self):
+        """NetworkInterface.current() should return cached interface within recheck interval."""
+        interface1 = NetworkInterface.current()
+        interface2 = NetworkInterface.current()
+
+        self.assertEqual(interface1.id, interface2.id)
+
+    def test_networkinterface_to_json(self):
+        """NetworkInterface.to_json() should serialize correctly."""
+        interface = NetworkInterface.current()
+        json_data = interface.to_json()
+
+        self.assertEqual(json_data['type'], 'NetworkInterface')
+        self.assertEqual(json_data['id'], str(interface.id))
+        self.assertEqual(json_data['machine_id'], str(interface.machine_id))
+        self.assertIn('ip_local', json_data)
+        self.assertIn('ip_public', json_data)
+
+    def test_networkinterface_manager_current(self):
+        """NetworkInterface.objects.current() should return current interface."""
+        interface = NetworkInterface.objects.current()
+        self.assertIsNotNone(interface)
+
+
+class TestBinaryModel(TestCase):
+    """Test the Binary model and BinaryMachine state machine."""
+
+    def setUp(self):
+        """Reset cached binaries and create a machine."""
+        import archivebox.machine.models as models
+        models._CURRENT_MACHINE = None
+        models._CURRENT_BINARIES = {}
+        self.machine = Machine.current()
+
+    def test_binary_creation(self):
+        """Binary should be created with default values."""
+        binary = Binary.objects.create(
+            machine=self.machine,
+            name='wget',
+            binproviders='apt,brew,env',
+        )
+
+        self.assertIsNotNone(binary.id)
+        self.assertEqual(binary.name, 'wget')
+        self.assertEqual(binary.status, Binary.StatusChoices.QUEUED)
+        self.assertFalse(binary.is_valid)
+
+    def test_binary_is_valid(self):
+        """Binary.is_valid should be True when abspath and version are set."""
+        binary = Binary.objects.create(
+            machine=self.machine,
+            name='wget',
+            abspath='/usr/bin/wget',
+            version='1.21',
+        )
+
+        self.assertTrue(binary.is_valid)
+
+    def test_binary_to_json(self):
+        """Binary.to_json() should serialize correctly."""
+        binary = Binary.objects.create(
+            machine=self.machine,
+            name='wget',
+            abspath='/usr/bin/wget',
+            version='1.21',
+            binprovider='apt',
+        )
+        json_data = binary.to_json()
+
+        self.assertEqual(json_data['type'], 'Binary')
+        self.assertEqual(json_data['name'], 'wget')
+        self.assertEqual(json_data['abspath'], '/usr/bin/wget')
+        self.assertEqual(json_data['version'], '1.21')
+
+    def test_binary_from_json_queued(self):
+        """Binary.from_json() should create queued binary from binaries.jsonl format."""
+        record = {
+            'name': 'curl',
+            'binproviders': 'apt,brew',
+            'overrides': {'apt': {'packages': ['curl']}},
+        }
+
+        binary = Binary.from_json(record)
+
+        self.assertIsNotNone(binary)
+        self.assertEqual(binary.name, 'curl')
+        self.assertEqual(binary.binproviders, 'apt,brew')
+        self.assertEqual(binary.status, Binary.StatusChoices.QUEUED)
+
+    def test_binary_from_json_installed(self):
+        """Binary.from_json() should update binary from hook output format."""
+        # First create queued binary
+        Binary.objects.create(
+            machine=self.machine,
+            name='node',
+        )
+
+        # Then update with hook output
+        record = {
+            'name': 'node',
+            'abspath': '/usr/bin/node',
+            'version': '18.0.0',
+            'binprovider': 'apt',
+        }
+
+        binary = Binary.from_json(record)
+
+        self.assertIsNotNone(binary)
+        self.assertEqual(binary.abspath, '/usr/bin/node')
+        self.assertEqual(binary.version, '18.0.0')
+        self.assertEqual(binary.status, Binary.StatusChoices.SUCCEEDED)
+
+    def test_binary_manager_get_valid_binary(self):
+        """BinaryManager.get_valid_binary() should find valid binaries."""
+        # Create invalid binary (no abspath)
+        Binary.objects.create(
+            machine=self.machine,
+            name='wget',
+        )
+
+        # Create valid binary
+        Binary.objects.create(
+            machine=self.machine,
+            name='wget',
+            abspath='/usr/bin/wget',
+            version='1.21',
+        )
+
+        result = Binary.objects.get_valid_binary('wget')
+
+        self.assertIsNotNone(result)
+        self.assertEqual(result.abspath, '/usr/bin/wget')
+
+    def test_binary_update_and_requeue(self):
+        """Binary.update_and_requeue() should update fields and save."""
+        binary = Binary.objects.create(
+            machine=self.machine,
+            name='test',
+        )
+        old_modified = binary.modified_at
+
+        binary.update_and_requeue(
+            status=Binary.StatusChoices.STARTED,
+            retry_at=timezone.now() + timedelta(seconds=60),
+        )
+
+        binary.refresh_from_db()
+        self.assertEqual(binary.status, Binary.StatusChoices.STARTED)
+        self.assertGreater(binary.modified_at, old_modified)
+
+
+class TestBinaryStateMachine(TestCase):
+    """Test the BinaryMachine state machine."""
+
+    def setUp(self):
+        """Create a machine and binary for state machine tests."""
+        import archivebox.machine.models as models
+        models._CURRENT_MACHINE = None
+        self.machine = Machine.current()
+        self.binary = Binary.objects.create(
+            machine=self.machine,
+            name='test-binary',
+            binproviders='env',
+        )
+
+    def test_binary_state_machine_initial_state(self):
+        """BinaryMachine should start in queued state."""
+        sm = BinaryMachine(self.binary)
+        self.assertEqual(sm.current_state.value, Binary.StatusChoices.QUEUED)
+
+    def test_binary_state_machine_can_start(self):
+        """BinaryMachine.can_start() should check name and binproviders."""
+        sm = BinaryMachine(self.binary)
+        self.assertTrue(sm.can_start())
+
+        # Binary without binproviders
+        self.binary.binproviders = ''
+        self.binary.save()
+        sm = BinaryMachine(self.binary)
+        self.assertFalse(sm.can_start())
+
+
+class TestProcessModel(TestCase):
+    """Test the Process model and ProcessMachine state machine."""
+
+    def setUp(self):
+        """Create a machine for process tests."""
+        import archivebox.machine.models as models
+        models._CURRENT_MACHINE = None
+        self.machine = Machine.current()
+
+    def test_process_creation(self):
+        """Process should be created with default values."""
+        process = Process.objects.create(
+            machine=self.machine,
+            cmd=['echo', 'hello'],
+            pwd='/tmp',
+        )
+
+        self.assertIsNotNone(process.id)
+        self.assertEqual(process.cmd, ['echo', 'hello'])
+        self.assertEqual(process.status, Process.StatusChoices.QUEUED)
+        self.assertIsNone(process.pid)
+        self.assertIsNone(process.exit_code)
+
+    def test_process_to_json(self):
+        """Process.to_json() should serialize correctly."""
+        process = Process.objects.create(
+            machine=self.machine,
+            cmd=['echo', 'hello'],
+            pwd='/tmp',
+            timeout=60,
+        )
+        json_data = process.to_json()
+
+        self.assertEqual(json_data['type'], 'Process')
+        self.assertEqual(json_data['cmd'], ['echo', 'hello'])
+        self.assertEqual(json_data['pwd'], '/tmp')
+        self.assertEqual(json_data['timeout'], 60)
+
+    def test_process_to_jsonl_with_binary(self):
+        """Process.to_jsonl() should include related binary."""
+        binary = Binary.objects.create(
+            machine=self.machine,
+            name='echo',
+            abspath='/bin/echo',
+            version='1.0',
+        )
+        process = Process.objects.create(
+            machine=self.machine,
+            cmd=['echo', 'hello'],
+            binary=binary,
+        )
+
+        records = list(process.to_jsonl(binary=True))
+
+        self.assertEqual(len(records), 2)
+        types = {r['type'] for r in records}
+        self.assertIn('Process', types)
+        self.assertIn('Binary', types)
+
+    def test_process_manager_create_for_archiveresult(self):
+        """ProcessManager.create_for_archiveresult() should create process."""
+        # This test would require an ArchiveResult, which is complex to set up
+        # For now, test the direct creation path
+        process = Process.objects.create(
+            machine=self.machine,
+            pwd='/tmp/test',
+            cmd=['wget', 'http://example.com'],
+            timeout=120,
+        )
+
+        self.assertEqual(process.pwd, '/tmp/test')
+        self.assertEqual(process.cmd, ['wget', 'http://example.com'])
+        self.assertEqual(process.timeout, 120)
+
+    def test_process_update_and_requeue(self):
+        """Process.update_and_requeue() should update fields and save."""
+        process = Process.objects.create(
+            machine=self.machine,
+            cmd=['test'],
+        )
+        old_modified = process.modified_at
+
+        process.update_and_requeue(
+            status=Process.StatusChoices.RUNNING,
+            pid=12345,
+            started_at=timezone.now(),
+        )
+
+        process.refresh_from_db()
+        self.assertEqual(process.status, Process.StatusChoices.RUNNING)
+        self.assertEqual(process.pid, 12345)
+        self.assertIsNotNone(process.started_at)
+
+
+class TestProcessStateMachine(TestCase):
+    """Test the ProcessMachine state machine."""
+
+    def setUp(self):
+        """Create a machine and process for state machine tests."""
+        import archivebox.machine.models as models
+        models._CURRENT_MACHINE = None
+        self.machine = Machine.current()
+        self.process = Process.objects.create(
+            machine=self.machine,
+            cmd=['echo', 'test'],
+            pwd='/tmp',
+        )
+
+    def test_process_state_machine_initial_state(self):
+        """ProcessMachine should start in queued state."""
+        sm = ProcessMachine(self.process)
+        self.assertEqual(sm.current_state.value, Process.StatusChoices.QUEUED)
+
+    def test_process_state_machine_can_start(self):
+        """ProcessMachine.can_start() should check cmd and machine."""
+        sm = ProcessMachine(self.process)
+        self.assertTrue(sm.can_start())
+
+        # Process without cmd
+        self.process.cmd = []
+        self.process.save()
+        sm = ProcessMachine(self.process)
+        self.assertFalse(sm.can_start())
+
+    def test_process_state_machine_is_exited(self):
+        """ProcessMachine.is_exited() should check exit_code."""
+        sm = ProcessMachine(self.process)
+        self.assertFalse(sm.is_exited())
+
+        self.process.exit_code = 0
+        self.process.save()
+        sm = ProcessMachine(self.process)
+        self.assertTrue(sm.is_exited())
+
+
+if __name__ == '__main__':
+    pytest.main([__file__, '-v'])
diff --git a/archivebox/plugins/apt/tests/__init__.py b/archivebox/plugins/apt/tests/__init__.py
new file mode 100644
index 00000000..fdde694e
--- /dev/null
+++ b/archivebox/plugins/apt/tests/__init__.py
@@ -0,0 +1 @@
+"""Tests for the apt binary provider plugin."""
diff --git a/archivebox/plugins/apt/tests/test_apt_provider.py b/archivebox/plugins/apt/tests/test_apt_provider.py
new file mode 100644
index 00000000..a5430a65
--- /dev/null
+++ b/archivebox/plugins/apt/tests/test_apt_provider.py
@@ -0,0 +1,177 @@
+"""
+Tests for the apt binary provider plugin.
+
+Tests cover:
+1. Hook script execution
+2. apt package availability detection
+3. JSONL output format
+"""
+
+import json
+import os
+import shutil
+import subprocess
+import sys
+import tempfile
+from pathlib import Path
+
+import pytest
+from django.test import TestCase
+
+
+# Get the path to the apt provider hook
+PLUGIN_DIR = Path(__file__).parent.parent
+INSTALL_HOOK = PLUGIN_DIR / 'on_Binary__install_using_apt_provider.py'
+
+
+def apt_available() -> bool:
+    """Check if apt is installed."""
+    return shutil.which('apt') is not None or shutil.which('apt-get') is not None
+
+
+def is_linux() -> bool:
+    """Check if running on Linux."""
+    import platform
+    return platform.system().lower() == 'linux'
+
+
+class TestAptProviderHook(TestCase):
+    """Test the apt binary provider installation hook."""
+
+    def setUp(self):
+        """Set up test environment."""
+        self.temp_dir = tempfile.mkdtemp()
+
+    def tearDown(self):
+        """Clean up."""
+        shutil.rmtree(self.temp_dir, ignore_errors=True)
+
+    def test_hook_script_exists(self):
+        """Hook script should exist."""
+        self.assertTrue(INSTALL_HOOK.exists(), f"Hook not found: {INSTALL_HOOK}")
+
+    def test_hook_skips_when_apt_not_allowed(self):
+        """Hook should skip when apt not in allowed binproviders."""
+        result = subprocess.run(
+            [
+                sys.executable, str(INSTALL_HOOK),
+                '--name=wget',
+                '--binary-id=test-uuid',
+                '--machine-id=test-machine',
+                '--binproviders=pip,npm',  # apt not allowed
+            ],
+            capture_output=True,
+            text=True,
+            timeout=30
+        )
+
+        # Should exit cleanly (code 0) when apt not allowed
+        self.assertIn('apt provider not allowed', result.stderr)
+        self.assertEqual(result.returncode, 0)
+
+    @pytest.mark.skipif(not is_linux(), reason="apt only available on Linux")
+    @pytest.mark.skipif(not apt_available(), reason="apt not installed")
+    def test_hook_detects_apt(self):
+        """Hook should detect apt binary when available."""
+        result = subprocess.run(
+            [
+                sys.executable, str(INSTALL_HOOK),
+                '--name=nonexistent-pkg-xyz123',
+                '--binary-id=test-uuid',
+                '--machine-id=test-machine',
+            ],
+            capture_output=True,
+            text=True,
+            timeout=30
+        )
+
+        # Should not say apt is not available
+        self.assertNotIn('apt not available', result.stderr)
+
+    def test_hook_handles_overrides(self):
+        """Hook should accept overrides JSON."""
+        overrides = json.dumps({
+            'apt': {'packages': ['custom-package-name']}
+        })
+
+        result = subprocess.run(
+            [
+                sys.executable, str(INSTALL_HOOK),
+                '--name=test-pkg',
+                '--binary-id=test-uuid',
+                '--machine-id=test-machine',
+                f'--overrides={overrides}',
+            ],
+            capture_output=True,
+            text=True,
+            timeout=30
+        )
+
+        # Should not crash parsing overrides
+        self.assertNotIn('Traceback', result.stderr)
+
+
+class TestAptProviderOutput(TestCase):
+    """Test JSONL output format from apt provider."""
+
+    def test_binary_record_format(self):
+        """Binary JSONL records should have required fields."""
+        record = {
+            'type': 'Binary',
+            'name': 'wget',
+            'abspath': '/usr/bin/wget',
+            'version': '1.21',
+            'binprovider': 'apt',
+            'sha256': '',
+            'machine_id': 'machine-uuid',
+            'binary_id': 'binary-uuid',
+        }
+
+        self.assertEqual(record['type'], 'Binary')
+        self.assertEqual(record['binprovider'], 'apt')
+        self.assertIn('name', record)
+        self.assertIn('abspath', record)
+        self.assertIn('version', record)
+
+
+@pytest.mark.skipif(not is_linux(), reason="apt only available on Linux")
+@pytest.mark.skipif(not apt_available(), reason="apt not installed")
+class TestAptProviderSystemBinaries(TestCase):
+    """Test apt provider with system binaries."""
+
+    def test_detect_existing_binary(self):
+        """apt provider should detect already-installed system binaries."""
+        # Check for a binary that's almost certainly installed (like 'ls' or 'bash')
+        result = subprocess.run(
+            [
+                sys.executable, str(INSTALL_HOOK),
+                '--name=bash',
+                '--binary-id=test-uuid',
+                '--machine-id=test-machine',
+            ],
+            capture_output=True,
+            text=True,
+            timeout=60
+        )
+
+        # Parse JSONL output
+        for line in result.stdout.split('\n'):
+            line = line.strip()
+            if line.startswith('{'):
+                try:
+                    record = json.loads(line)
+                    if record.get('type') == 'Binary' and record.get('name') == 'bash':
+                        # Found bash
+                        self.assertTrue(record.get('abspath'))
+                        self.assertTrue(Path(record['abspath']).exists())
+                        return
+                except json.JSONDecodeError:
+                    continue
+
+        # apt may not be able to "install" bash (already installed)
+        # Just verify no crash
+        self.assertNotIn('Traceback', result.stderr)
+
+
+if __name__ == '__main__':
+    pytest.main([__file__, '-v'])
diff --git a/archivebox/plugins/npm/tests/__init__.py b/archivebox/plugins/npm/tests/__init__.py
new file mode 100644
index 00000000..08ccd028
--- /dev/null
+++ b/archivebox/plugins/npm/tests/__init__.py
@@ -0,0 +1 @@
+"""Tests for the npm binary provider plugin."""
diff --git a/archivebox/plugins/npm/tests/test_npm_provider.py b/archivebox/plugins/npm/tests/test_npm_provider.py
new file mode 100644
index 00000000..99057336
--- /dev/null
+++ b/archivebox/plugins/npm/tests/test_npm_provider.py
@@ -0,0 +1,223 @@
+"""
+Tests for the npm binary provider plugin.
+
+Tests cover:
+1. Hook script execution
+2. npm package installation
+3. PATH and NODE_MODULES_DIR updates
+4. JSONL output format
+"""
+
+import json
+import os
+import shutil
+import subprocess
+import sys
+import tempfile
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+from django.test import TestCase
+
+
+# Get the path to the npm provider hook
+PLUGIN_DIR = Path(__file__).parent.parent
+INSTALL_HOOK = PLUGIN_DIR / 'on_Binary__install_using_npm_provider.py'
+
+
+def npm_available() -> bool:
+    """Check if npm is installed."""
+    return shutil.which('npm') is not None
+
+
+class TestNpmProviderHook(TestCase):
+    """Test the npm binary provider installation hook."""
+
+    def setUp(self):
+        """Set up test environment."""
+        self.temp_dir = tempfile.mkdtemp()
+        self.lib_dir = Path(self.temp_dir) / 'lib' / 'x86_64-linux'
+        self.lib_dir.mkdir(parents=True)
+
+    def tearDown(self):
+        """Clean up."""
+        shutil.rmtree(self.temp_dir, ignore_errors=True)
+
+    def test_hook_script_exists(self):
+        """Hook script should exist."""
+        self.assertTrue(INSTALL_HOOK.exists(), f"Hook not found: {INSTALL_HOOK}")
+
+    def test_hook_requires_lib_dir(self):
+        """Hook should fail when LIB_DIR is not set."""
+        env = os.environ.copy()
+        env.pop('LIB_DIR', None)  # Remove LIB_DIR
+
+        result = subprocess.run(
+            [
+                sys.executable, str(INSTALL_HOOK),
+                '--name=some-package',
+                '--binary-id=test-uuid',
+                '--machine-id=test-machine',
+            ],
+            capture_output=True,
+            text=True,
+            env=env,
+            timeout=30
+        )
+
+        self.assertIn('LIB_DIR environment variable not set', result.stderr)
+        self.assertEqual(result.returncode, 1)
+
+    def test_hook_skips_when_npm_not_allowed(self):
+        """Hook should skip when npm not in allowed binproviders."""
+        env = os.environ.copy()
+        env['LIB_DIR'] = str(self.lib_dir)
+
+        result = subprocess.run(
+            [
+                sys.executable, str(INSTALL_HOOK),
+                '--name=some-package',
+                '--binary-id=test-uuid',
+                '--machine-id=test-machine',
+                '--binproviders=pip,apt',  # npm not allowed
+            ],
+            capture_output=True,
+            text=True,
+            env=env,
+            timeout=30
+        )
+
+        # Should exit cleanly (code 0) when npm not allowed
+        self.assertIn('npm provider not allowed', result.stderr)
+        self.assertEqual(result.returncode, 0)
+
+    @pytest.mark.skipif(not npm_available(), reason="npm not installed")
+    def test_hook_creates_npm_prefix(self):
+        """Hook should create npm prefix directory."""
+        env = os.environ.copy()
+        env['LIB_DIR'] = str(self.lib_dir)
+
+        # Even if installation fails, the npm prefix should be created
+        subprocess.run(
+            [
+                sys.executable, str(INSTALL_HOOK),
+                '--name=nonexistent-xyz123',
+                '--binary-id=test-uuid',
+                '--machine-id=test-machine',
+            ],
+            capture_output=True,
+            text=True,
+            env=env,
+            timeout=60
+        )
+
+        npm_prefix = self.lib_dir / 'npm'
+        self.assertTrue(npm_prefix.exists())
+
+    def test_hook_handles_overrides(self):
+        """Hook should accept overrides JSON."""
+        env = os.environ.copy()
+        env['LIB_DIR'] = str(self.lib_dir)
+
+        overrides = json.dumps({'npm': {'packages': ['custom-pkg']}})
+
+        # Just verify it doesn't crash with overrides
+        result = subprocess.run(
+            [
+                sys.executable, str(INSTALL_HOOK),
+                '--name=test-pkg',
+                '--binary-id=test-uuid',
+                '--machine-id=test-machine',
+                f'--overrides={overrides}',
+            ],
+            capture_output=True,
+            text=True,
+            env=env,
+            timeout=60
+        )
+
+        # May fail to install, but should not crash parsing overrides
+        self.assertNotIn('Failed to parse overrides JSON', result.stderr)
+
+
+class TestNpmProviderOutput(TestCase):
+    """Test JSONL output format from npm provider."""
+
+    def test_binary_record_format(self):
+        """Binary JSONL records should have required fields."""
+        record = {
+            'type': 'Binary',
+            'name': 'prettier',
+            'abspath': '/path/to/node_modules/.bin/prettier',
+            'version': '3.0.0',
+            'binprovider': 'npm',
+            'sha256': '',
+            'machine_id': 'machine-uuid',
+            'binary_id': 'binary-uuid',
+        }
+
+        self.assertEqual(record['type'], 'Binary')
+        self.assertEqual(record['binprovider'], 'npm')
+        self.assertIn('abspath', record)
+
+    def test_machine_update_record_format(self):
+        """Machine update records should have correct format."""
+        record = {
+            'type': 'Machine',
+            '_method': 'update',
+            'key': 'config/PATH',
+            'value': '/path/to/npm/bin:/existing/path',
+        }
+
+        self.assertEqual(record['type'], 'Machine')
+        self.assertEqual(record['_method'], 'update')
+        self.assertIn('key', record)
+        self.assertIn('value', record)
+
+    def test_node_modules_dir_record_format(self):
+        """NODE_MODULES_DIR update record should have correct format."""
+        record = {
+            'type': 'Machine',
+            '_method': 'update',
+            'key': 'config/NODE_MODULES_DIR',
+            'value': '/path/to/npm/node_modules',
+        }
+
+        self.assertEqual(record['key'], 'config/NODE_MODULES_DIR')
+
+
+@pytest.mark.skipif(not npm_available(), reason="npm not installed")
+class TestNpmProviderIntegration(TestCase):
+    """Integration tests with real npm installations."""
+
+    def setUp(self):
+        """Set up isolated npm environment."""
+        self.temp_dir = tempfile.mkdtemp()
+        self.lib_dir = Path(self.temp_dir) / 'lib' / 'x86_64-linux'
+        self.lib_dir.mkdir(parents=True)
+
+    def tearDown(self):
+        """Clean up."""
+        shutil.rmtree(self.temp_dir, ignore_errors=True)
+
+    def test_npm_prefix_structure(self):
+        """Verify npm creates expected directory structure."""
+        npm_prefix = self.lib_dir / 'npm'
+        npm_prefix.mkdir(parents=True)
+
+        # Expected structure after npm install:
+        # npm/
+        #   bin/  (symlinks to binaries)
+        #   node_modules/  (packages)
+
+        expected_dirs = ['bin', 'node_modules']
+        for dir_name in expected_dirs:
+            (npm_prefix / dir_name).mkdir(exist_ok=True)
+
+        for dir_name in expected_dirs:
+            self.assertTrue((npm_prefix / dir_name).exists())
+
+
+if __name__ == '__main__':
+    pytest.main([__file__, '-v'])
diff --git a/archivebox/plugins/pip/tests/__init__.py b/archivebox/plugins/pip/tests/__init__.py
new file mode 100644
index 00000000..28ac0d82
--- /dev/null
+++ b/archivebox/plugins/pip/tests/__init__.py
@@ -0,0 +1 @@
+"""Tests for the pip binary provider plugin."""
diff --git a/archivebox/plugins/pip/tests/test_pip_provider.py b/archivebox/plugins/pip/tests/test_pip_provider.py
new file mode 100644
index 00000000..3a63f84b
--- /dev/null
+++ b/archivebox/plugins/pip/tests/test_pip_provider.py
@@ -0,0 +1,198 @@
+"""
+Tests for the pip binary provider plugin.
+
+Tests cover:
+1. Hook script execution
+2. pip package detection
+3. Virtual environment handling
+4. JSONL output format
+"""
+
+import json
+import os
+import subprocess
+import sys
+import tempfile
+from pathlib import Path
+from unittest.mock import patch, MagicMock
+
+import pytest
+from django.test import TestCase
+
+
+# Get the path to the pip provider hook
+PLUGIN_DIR = Path(__file__).parent.parent
+INSTALL_HOOK = PLUGIN_DIR / 'on_Binary__install_using_pip_provider.py'
+
+
+class TestPipProviderHook(TestCase):
+    """Test the pip binary provider installation hook."""
+
+    def setUp(self):
+        """Set up test environment."""
+        self.temp_dir = tempfile.mkdtemp()
+        self.output_dir = Path(self.temp_dir) / 'output'
+        self.output_dir.mkdir()
+
+    def tearDown(self):
+        """Clean up."""
+        import shutil
+        shutil.rmtree(self.temp_dir, ignore_errors=True)
+
+    def test_hook_script_exists(self):
+        """Hook script should exist."""
+        self.assertTrue(INSTALL_HOOK.exists(), f"Hook not found: {INSTALL_HOOK}")
+
+    def test_hook_help(self):
+        """Hook should accept --help without error."""
+        result = subprocess.run(
+            [sys.executable, str(INSTALL_HOOK), '--help'],
+            capture_output=True,
+            text=True,
+            timeout=30
+        )
+        # May succeed or fail depending on implementation
+        # At minimum should not crash with Python error
+        self.assertNotIn('Traceback', result.stderr)
+
+    def test_hook_finds_python(self):
+        """Hook should find Python binary."""
+        env = os.environ.copy()
+        env['DATA_DIR'] = self.temp_dir
+
+        result = subprocess.run(
+            [
+                sys.executable, str(INSTALL_HOOK),
+                '--name=python3',
+                '--binproviders=pip,env',
+            ],
+            capture_output=True,
+            text=True,
+            cwd=str(self.output_dir),
+            env=env,
+            timeout=60
+        )
+
+        # Check for JSONL output
+        jsonl_found = False
+        for line in result.stdout.split('\n'):
+            line = line.strip()
+            if line.startswith('{'):
+                try:
+                    record = json.loads(line)
+                    if record.get('type') == 'Binary' and record.get('name') == 'python3':
+                        jsonl_found = True
+                        # Verify structure
+                        self.assertIn('abspath', record)
+                        self.assertIn('version', record)
+                        break
+                except json.JSONDecodeError:
+                    continue
+
+        # May or may not find python3 via pip, but should not crash
+        self.assertNotIn('Traceback', result.stderr)
+
+    def test_hook_unknown_package(self):
+        """Hook should handle unknown packages gracefully."""
+        env = os.environ.copy()
+        env['DATA_DIR'] = self.temp_dir
+
+        result = subprocess.run(
+            [
+                sys.executable, str(INSTALL_HOOK),
+                '--name=nonexistent_package_xyz123',
+                '--binproviders=pip',
+            ],
+            capture_output=True,
+            text=True,
+            cwd=str(self.output_dir),
+            env=env,
+            timeout=60
+        )
+
+        # Should not crash
+        self.assertNotIn('Traceback', result.stderr)
+        # May have non-zero exit code for missing package
+
+
+class TestPipProviderIntegration(TestCase):
+    """Integration tests for pip provider with real packages."""
+
+    def setUp(self):
+        """Set up test environment."""
+        self.temp_dir = tempfile.mkdtemp()
+        self.output_dir = Path(self.temp_dir) / 'output'
+        self.output_dir.mkdir()
+
+    def tearDown(self):
+        """Clean up."""
+        import shutil
+        shutil.rmtree(self.temp_dir, ignore_errors=True)
+
+    @pytest.mark.skipif(
+        subprocess.run([sys.executable, '-m', 'pip', '--version'],
+                       capture_output=True).returncode != 0,
+        reason="pip not available"
+    )
+    def test_hook_finds_pip_installed_binary(self):
+        """Hook should find binaries installed via pip."""
+        env = os.environ.copy()
+        env['DATA_DIR'] = self.temp_dir
+
+        # Try to find 'pip' itself which should be available
+        result = subprocess.run(
+            [
+                sys.executable, str(INSTALL_HOOK),
+                '--name=pip',
+                '--binproviders=pip,env',
+            ],
+            capture_output=True,
+            text=True,
+            cwd=str(self.output_dir),
+            env=env,
+            timeout=60
+        )
+
+        # Look for success in output
+        for line in result.stdout.split('\n'):
+            line = line.strip()
+            if line.startswith('{'):
+                try:
+                    record = json.loads(line)
+                    if record.get('type') == 'Binary' and 'pip' in record.get('name', ''):
+                        # Found pip binary
+                        self.assertTrue(record.get('abspath'))
+                        return
+                except json.JSONDecodeError:
+                    continue
+
+        # If we get here without finding pip, that's acceptable
+        # as long as the hook didn't crash
+        self.assertNotIn('Traceback', result.stderr)
+
+
+class TestPipProviderOutput(TestCase):
+    """Test JSONL output format from pip provider."""
+
+    def test_binary_record_format(self):
+        """Binary JSONL records should have required fields."""
+        # Example of expected format
+        record = {
+            'type': 'Binary',
+            'name': 'wget',
+            'abspath': '/usr/bin/wget',
+            'version': '1.21',
+            'binprovider': 'pip',
+            'sha256': 'abc123...',
+        }
+
+        # Validate structure
+        self.assertEqual(record['type'], 'Binary')
+        self.assertIn('name', record)
+        self.assertIn('abspath', record)
+        self.assertIn('version', record)
+        self.assertIn('binprovider', record)
+
+
+if __name__ == '__main__':
+    pytest.main([__file__, '-v'])
diff --git a/archivebox/plugins/search_backend_ripgrep/tests/test_ripgrep_search.py b/archivebox/plugins/search_backend_ripgrep/tests/test_ripgrep_search.py
new file mode 100644
index 00000000..75513d34
--- /dev/null
+++ b/archivebox/plugins/search_backend_ripgrep/tests/test_ripgrep_search.py
@@ -0,0 +1,308 @@
+"""
+Tests for the ripgrep search backend.
+
+Tests cover:
+1. Search with ripgrep binary
+2. Snapshot ID extraction from file paths
+3. Timeout handling
+4. Error handling
+5. Environment variable configuration
+"""
+
+import os
+import shutil
+import subprocess
+import tempfile
+from pathlib import Path
+from unittest.mock import patch, MagicMock
+
+import pytest
+from django.test import TestCase
+
+from archivebox.plugins.search_backend_ripgrep.search import (
+    search,
+    flush,
+    get_env,
+    get_env_int,
+    get_env_array,
+)
+
+
+class TestEnvHelpers(TestCase):
+    """Test environment variable helper functions."""
+
+    def test_get_env_default(self):
+        """get_env should return default for unset vars."""
+        result = get_env('NONEXISTENT_VAR_12345', 'default')
+        self.assertEqual(result, 'default')
+
+    def test_get_env_set(self):
+        """get_env should return value for set vars."""
+        with patch.dict(os.environ, {'TEST_VAR': 'value'}):
+            result = get_env('TEST_VAR', 'default')
+            self.assertEqual(result, 'value')
+
+    def test_get_env_strips_whitespace(self):
+        """get_env should strip whitespace."""
+        with patch.dict(os.environ, {'TEST_VAR': '  value  '}):
+            result = get_env('TEST_VAR', '')
+            self.assertEqual(result, 'value')
+
+    def test_get_env_int_default(self):
+        """get_env_int should return default for unset vars."""
+        result = get_env_int('NONEXISTENT_VAR_12345', 42)
+        self.assertEqual(result, 42)
+
+    def test_get_env_int_valid(self):
+        """get_env_int should parse integer values."""
+        with patch.dict(os.environ, {'TEST_INT': '100'}):
+            result = get_env_int('TEST_INT', 0)
+            self.assertEqual(result, 100)
+
+    def test_get_env_int_invalid(self):
+        """get_env_int should return default for invalid integers."""
+        with patch.dict(os.environ, {'TEST_INT': 'not a number'}):
+            result = get_env_int('TEST_INT', 42)
+            self.assertEqual(result, 42)
+
+    def test_get_env_array_default(self):
+        """get_env_array should return default for unset vars."""
+        result = get_env_array('NONEXISTENT_VAR_12345', ['default'])
+        self.assertEqual(result, ['default'])
+
+    def test_get_env_array_valid(self):
+        """get_env_array should parse JSON arrays."""
+        with patch.dict(os.environ, {'TEST_ARRAY': '["a", "b", "c"]'}):
+            result = get_env_array('TEST_ARRAY', [])
+            self.assertEqual(result, ['a', 'b', 'c'])
+
+    def test_get_env_array_invalid_json(self):
+        """get_env_array should return default for invalid JSON."""
+        with patch.dict(os.environ, {'TEST_ARRAY': 'not json'}):
+            result = get_env_array('TEST_ARRAY', ['default'])
+            self.assertEqual(result, ['default'])
+
+    def test_get_env_array_not_array(self):
+        """get_env_array should return default for non-array JSON."""
+        with patch.dict(os.environ, {'TEST_ARRAY': '{"key": "value"}'}):
+            result = get_env_array('TEST_ARRAY', ['default'])
+            self.assertEqual(result, ['default'])
+
+
+class TestRipgrepFlush(TestCase):
+    """Test the flush function."""
+
+    def test_flush_is_noop(self):
+        """flush should be a no-op for ripgrep backend."""
+        # Should not raise
+        flush(['snap-001', 'snap-002'])
+
+
+class TestRipgrepSearch(TestCase):
+    """Test the ripgrep search function."""
+
+    def setUp(self):
+        """Create temporary archive directory with test files."""
+        self.temp_dir = tempfile.mkdtemp()
+        self.archive_dir = Path(self.temp_dir) / 'archive'
+        self.archive_dir.mkdir()
+
+        # Create snapshot directories with searchable content
+        self._create_snapshot('snap-001', {
+            'singlefile/index.html': '<html><body>Python programming tutorial</body></html>',
+            'title/title.txt': 'Learn Python Programming',
+        })
+        self._create_snapshot('snap-002', {
+            'singlefile/index.html': '<html><body>JavaScript guide</body></html>',
+            'title/title.txt': 'JavaScript Basics',
+        })
+        self._create_snapshot('snap-003', {
+            'wget/index.html': '<html><body>Web archiving best practices</body></html>',
+            'title/title.txt': 'Web Archiving Guide',
+        })
+
+        # Patch settings
+        self.settings_patch = patch(
+            'archivebox.plugins.search_backend_ripgrep.search.settings'
+        )
+        self.mock_settings = self.settings_patch.start()
+        self.mock_settings.ARCHIVE_DIR = str(self.archive_dir)
+
+    def tearDown(self):
+        """Clean up temporary directory."""
+        self.settings_patch.stop()
+        shutil.rmtree(self.temp_dir, ignore_errors=True)
+
+    def _create_snapshot(self, snapshot_id: str, files: dict):
+        """Create a snapshot directory with files."""
+        snap_dir = self.archive_dir / snapshot_id
+        for path, content in files.items():
+            file_path = snap_dir / path
+            file_path.parent.mkdir(parents=True, exist_ok=True)
+            file_path.write_text(content)
+
+    def _has_ripgrep(self) -> bool:
+        """Check if ripgrep is available."""
+        return shutil.which('rg') is not None
+
+    def test_search_no_archive_dir(self):
+        """search should return empty list when archive dir doesn't exist."""
+        self.mock_settings.ARCHIVE_DIR = '/nonexistent/path'
+        results = search('test')
+        self.assertEqual(results, [])
+
+    @pytest.mark.skipif(not shutil.which('rg'), reason="ripgrep not installed")
+    def test_search_single_match(self):
+        """search should find matching snapshot."""
+        results = search('Python programming')
+
+        self.assertIn('snap-001', results)
+        self.assertNotIn('snap-002', results)
+        self.assertNotIn('snap-003', results)
+
+    @pytest.mark.skipif(not shutil.which('rg'), reason="ripgrep not installed")
+    def test_search_multiple_matches(self):
+        """search should find all matching snapshots."""
+        # 'guide' appears in snap-002 (JavaScript guide) and snap-003 (Archiving Guide)
+        results = search('guide')
+
+        self.assertIn('snap-002', results)
+        self.assertIn('snap-003', results)
+        self.assertNotIn('snap-001', results)
+
+    @pytest.mark.skipif(not shutil.which('rg'), reason="ripgrep not installed")
+    def test_search_case_insensitive_by_default(self):
+        """search should be case-sensitive (ripgrep default)."""
+        # By default rg is case-sensitive
+        results_upper = search('PYTHON')
+        results_lower = search('python')
+
+        # Depending on ripgrep config, results may differ
+        self.assertIsInstance(results_upper, list)
+        self.assertIsInstance(results_lower, list)
+
+    @pytest.mark.skipif(not shutil.which('rg'), reason="ripgrep not installed")
+    def test_search_no_results(self):
+        """search should return empty list for no matches."""
+        results = search('xyznonexistent123')
+        self.assertEqual(results, [])
+
+    @pytest.mark.skipif(not shutil.which('rg'), reason="ripgrep not installed")
+    def test_search_regex(self):
+        """search should support regex patterns."""
+        results = search('(Python|JavaScript)')
+
+        self.assertIn('snap-001', results)
+        self.assertIn('snap-002', results)
+
+    @pytest.mark.skipif(not shutil.which('rg'), reason="ripgrep not installed")
+    def test_search_distinct_snapshots(self):
+        """search should return distinct snapshot IDs."""
+        # Query matches both files in snap-001
+        results = search('Python')
+
+        # Should only appear once
+        self.assertEqual(results.count('snap-001'), 1)
+
+    def test_search_missing_binary(self):
+        """search should raise when ripgrep binary not found."""
+        with patch.dict(os.environ, {'RIPGREP_BINARY': '/nonexistent/rg'}):
+            with patch('shutil.which', return_value=None):
+                with self.assertRaises(RuntimeError) as context:
+                    search('test')
+                self.assertIn('ripgrep binary not found', str(context.exception))
+
+    @pytest.mark.skipif(not shutil.which('rg'), reason="ripgrep not installed")
+    def test_search_with_custom_args(self):
+        """search should use custom RIPGREP_ARGS."""
+        with patch.dict(os.environ, {'RIPGREP_ARGS': '["-i"]'}):  # Case insensitive
+            results = search('PYTHON')
+            # With -i flag, should find regardless of case
+            self.assertIn('snap-001', results)
+
+    @pytest.mark.skipif(not shutil.which('rg'), reason="ripgrep not installed")
+    def test_search_timeout(self):
+        """search should handle timeout gracefully."""
+        with patch.dict(os.environ, {'RIPGREP_TIMEOUT': '1'}):
+            # Short timeout, should still complete for small archive
+            results = search('Python')
+            self.assertIsInstance(results, list)
+
+
+class TestRipgrepSearchIntegration(TestCase):
+    """Integration tests with realistic archive structure."""
+
+    def setUp(self):
+        """Create archive with realistic structure."""
+        self.temp_dir = tempfile.mkdtemp()
+        self.archive_dir = Path(self.temp_dir) / 'archive'
+        self.archive_dir.mkdir()
+
+        # Realistic snapshot structure
+        self._create_snapshot('1704067200.123456', {  # 2024-01-01
+            'singlefile.html': '''<!DOCTYPE html>
+<html>
+<head><title>ArchiveBox Documentation</title></head>
+<body>
+<h1>Getting Started with ArchiveBox</h1>
+<p>ArchiveBox is a powerful, self-hosted web archiving tool.</p>
+<p>Install with: pip install archivebox</p>
+</body>
+</html>''',
+            'title/title.txt': 'ArchiveBox Documentation',
+            'screenshot/screenshot.png': b'PNG IMAGE DATA',  # Binary file
+        })
+        self._create_snapshot('1704153600.654321', {  # 2024-01-02
+            'wget/index.html': '''<html>
+<head><title>Python News</title></head>
+<body>
+<h1>Python 3.12 Released</h1>
+<p>New features include improved error messages and performance.</p>
+</body>
+</html>''',
+            'readability/content.html': '<p>Python 3.12 has been released with exciting new features.</p>',
+        })
+
+        self.settings_patch = patch(
+            'archivebox.plugins.search_backend_ripgrep.search.settings'
+        )
+        self.mock_settings = self.settings_patch.start()
+        self.mock_settings.ARCHIVE_DIR = str(self.archive_dir)
+
+    def tearDown(self):
+        """Clean up."""
+        self.settings_patch.stop()
+        shutil.rmtree(self.temp_dir, ignore_errors=True)
+
+    def _create_snapshot(self, timestamp: str, files: dict):
+        """Create snapshot with timestamp-based ID."""
+        snap_dir = self.archive_dir / timestamp
+        for path, content in files.items():
+            file_path = snap_dir / path
+            file_path.parent.mkdir(parents=True, exist_ok=True)
+            if isinstance(content, bytes):
+                file_path.write_bytes(content)
+            else:
+                file_path.write_text(content)
+
+    @pytest.mark.skipif(not shutil.which('rg'), reason="ripgrep not installed")
+    def test_search_archivebox(self):
+        """Search for archivebox should find documentation snapshot."""
+        results = search('archivebox')
+        self.assertIn('1704067200.123456', results)
+
+    @pytest.mark.skipif(not shutil.which('rg'), reason="ripgrep not installed")
+    def test_search_python(self):
+        """Search for python should find Python news snapshot."""
+        results = search('Python')
+        self.assertIn('1704153600.654321', results)
+
+    @pytest.mark.skipif(not shutil.which('rg'), reason="ripgrep not installed")
+    def test_search_pip_install(self):
+        """Search for installation command."""
+        results = search('pip install')
+        self.assertIn('1704067200.123456', results)
+
+
+if __name__ == '__main__':
+    pytest.main([__file__, '-v'])
diff --git a/archivebox/plugins/search_backend_sqlite/tests/__init__.py b/archivebox/plugins/search_backend_sqlite/tests/__init__.py
new file mode 100644
index 00000000..6bef82e4
--- /dev/null
+++ b/archivebox/plugins/search_backend_sqlite/tests/__init__.py
@@ -0,0 +1 @@
+"""Tests for the SQLite FTS5 search backend."""
diff --git a/archivebox/plugins/search_backend_sqlite/tests/test_sqlite_search.py b/archivebox/plugins/search_backend_sqlite/tests/test_sqlite_search.py
new file mode 100644
index 00000000..ea12b85f
--- /dev/null
+++ b/archivebox/plugins/search_backend_sqlite/tests/test_sqlite_search.py
@@ -0,0 +1,351 @@
+"""
+Tests for the SQLite FTS5 search backend.
+
+Tests cover:
+1. Search index creation
+2. Indexing snapshots
+3. Search queries with real test data
+4. Flush operations
+5. Edge cases (empty index, special characters)
+"""
+
+import os
+import sqlite3
+import tempfile
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+from django.test import TestCase, override_settings
+
+from archivebox.plugins.search_backend_sqlite.search import (
+    get_db_path,
+    search,
+    flush,
+    SQLITEFTS_DB,
+    FTS_TOKENIZERS,
+)
+
+
+class TestSqliteSearchBackend(TestCase):
+    """Test SQLite FTS5 search backend."""
+
+    def setUp(self):
+        """Create a temporary data directory with search index."""
+        self.temp_dir = tempfile.mkdtemp()
+        self.db_path = Path(self.temp_dir) / 'search.sqlite3'
+
+        # Patch DATA_DIR
+        self.settings_patch = patch(
+            'archivebox.plugins.search_backend_sqlite.search.settings'
+        )
+        self.mock_settings = self.settings_patch.start()
+        self.mock_settings.DATA_DIR = self.temp_dir
+
+        # Create FTS5 table
+        self._create_index()
+
+    def tearDown(self):
+        """Clean up temporary directory."""
+        self.settings_patch.stop()
+        import shutil
+        shutil.rmtree(self.temp_dir, ignore_errors=True)
+
+    def _create_index(self):
+        """Create the FTS5 search index table."""
+        conn = sqlite3.connect(str(self.db_path))
+        try:
+            conn.execute(f'''
+                CREATE VIRTUAL TABLE IF NOT EXISTS search_index
+                USING fts5(
+                    snapshot_id,
+                    url,
+                    title,
+                    content,
+                    tokenize = '{FTS_TOKENIZERS}'
+                )
+            ''')
+            conn.commit()
+        finally:
+            conn.close()
+
+    def _index_snapshot(self, snapshot_id: str, url: str, title: str, content: str):
+        """Add a snapshot to the index."""
+        conn = sqlite3.connect(str(self.db_path))
+        try:
+            conn.execute(
+                'INSERT INTO search_index (snapshot_id, url, title, content) VALUES (?, ?, ?, ?)',
+                (snapshot_id, url, title, content)
+            )
+            conn.commit()
+        finally:
+            conn.close()
+
+    def test_get_db_path(self):
+        """get_db_path should return correct path."""
+        path = get_db_path()
+        self.assertEqual(path, Path(self.temp_dir) / SQLITEFTS_DB)
+
+    def test_search_empty_index(self):
+        """search should return empty list for empty index."""
+        results = search('nonexistent')
+        self.assertEqual(results, [])
+
+    def test_search_no_index_file(self):
+        """search should return empty list when index file doesn't exist."""
+        os.remove(self.db_path)
+        results = search('test')
+        self.assertEqual(results, [])
+
+    def test_search_single_result(self):
+        """search should find matching snapshot."""
+        self._index_snapshot(
+            'snap-001',
+            'https://example.com/page1',
+            'Example Page',
+            'This is example content about testing.'
+        )
+
+        results = search('example')
+        self.assertEqual(len(results), 1)
+        self.assertEqual(results[0], 'snap-001')
+
+    def test_search_multiple_results(self):
+        """search should find all matching snapshots."""
+        self._index_snapshot('snap-001', 'https://example.com/1', 'Python Tutorial', 'Learn Python programming')
+        self._index_snapshot('snap-002', 'https://example.com/2', 'Python Guide', 'Advanced Python concepts')
+        self._index_snapshot('snap-003', 'https://example.com/3', 'JavaScript Basics', 'Learn JavaScript')
+
+        results = search('Python')
+        self.assertEqual(len(results), 2)
+        self.assertIn('snap-001', results)
+        self.assertIn('snap-002', results)
+        self.assertNotIn('snap-003', results)
+
+    def test_search_title_match(self):
+        """search should match against title."""
+        self._index_snapshot('snap-001', 'https://example.com', 'Django Web Framework', 'Content here')
+
+        results = search('Django')
+        self.assertEqual(len(results), 1)
+        self.assertEqual(results[0], 'snap-001')
+
+    def test_search_url_match(self):
+        """search should match against URL."""
+        self._index_snapshot('snap-001', 'https://archivebox.io/docs', 'Title', 'Content')
+
+        results = search('archivebox')
+        self.assertEqual(len(results), 1)
+
+    def test_search_content_match(self):
+        """search should match against content."""
+        self._index_snapshot(
+            'snap-001',
+            'https://example.com',
+            'Generic Title',
+            'This document contains information about cryptography and security.'
+        )
+
+        results = search('cryptography')
+        self.assertEqual(len(results), 1)
+
+    def test_search_case_insensitive(self):
+        """search should be case insensitive."""
+        self._index_snapshot('snap-001', 'https://example.com', 'Title', 'PYTHON programming')
+
+        results = search('python')
+        self.assertEqual(len(results), 1)
+
+    def test_search_stemming(self):
+        """search should use porter stemmer for word stems."""
+        self._index_snapshot('snap-001', 'https://example.com', 'Title', 'Programming concepts')
+
+        # 'program' should match 'programming' with porter stemmer
+        results = search('program')
+        self.assertEqual(len(results), 1)
+
+    def test_search_multiple_words(self):
+        """search should match documents with all words."""
+        self._index_snapshot('snap-001', 'https://example.com', 'Web Development', 'Learn web development skills')
+        self._index_snapshot('snap-002', 'https://example.com', 'Web Design', 'Design beautiful websites')
+
+        results = search('web development')
+        # FTS5 defaults to OR, so both might match
+        # With porter stemmer, both should match 'web'
+        self.assertIn('snap-001', results)
+
+    def test_search_phrase(self):
+        """search should support phrase queries."""
+        self._index_snapshot('snap-001', 'https://example.com', 'Title', 'machine learning algorithms')
+        self._index_snapshot('snap-002', 'https://example.com', 'Title', 'machine algorithms learning')
+
+        # Phrase search with quotes
+        results = search('"machine learning"')
+        self.assertEqual(len(results), 1)
+        self.assertEqual(results[0], 'snap-001')
+
+    def test_search_distinct_results(self):
+        """search should return distinct snapshot IDs."""
+        # Index same snapshot twice (could happen with multiple fields matching)
+        self._index_snapshot('snap-001', 'https://python.org', 'Python', 'Python programming language')
+
+        results = search('Python')
+        self.assertEqual(len(results), 1)
+
+    def test_flush_single(self):
+        """flush should remove snapshot from index."""
+        self._index_snapshot('snap-001', 'https://example.com', 'Title', 'Content')
+        self._index_snapshot('snap-002', 'https://example.com', 'Title', 'Content')
+
+        flush(['snap-001'])
+
+        results = search('Content')
+        self.assertEqual(len(results), 1)
+        self.assertEqual(results[0], 'snap-002')
+
+    def test_flush_multiple(self):
+        """flush should remove multiple snapshots."""
+        self._index_snapshot('snap-001', 'https://example.com', 'Title', 'Test')
+        self._index_snapshot('snap-002', 'https://example.com', 'Title', 'Test')
+        self._index_snapshot('snap-003', 'https://example.com', 'Title', 'Test')
+
+        flush(['snap-001', 'snap-003'])
+
+        results = search('Test')
+        self.assertEqual(len(results), 1)
+        self.assertEqual(results[0], 'snap-002')
+
+    def test_flush_nonexistent(self):
+        """flush should not raise for nonexistent snapshots."""
+        # Should not raise
+        flush(['nonexistent-snap'])
+
+    def test_flush_no_index(self):
+        """flush should not raise when index doesn't exist."""
+        os.remove(self.db_path)
+        # Should not raise
+        flush(['snap-001'])
+
+    def test_search_special_characters(self):
+        """search should handle special characters in queries."""
+        self._index_snapshot('snap-001', 'https://example.com', 'C++ Programming', 'Learn C++ basics')
+
+        # FTS5 handles special chars
+        results = search('C++')
+        # May or may not match depending on tokenizer config
+        # At minimum, should not raise
+        self.assertIsInstance(results, list)
+
+    def test_search_unicode(self):
+        """search should handle unicode content."""
+        self._index_snapshot('snap-001', 'https://example.com', 'Titre Francais', 'cafe resume')
+        self._index_snapshot('snap-002', 'https://example.com', 'Japanese', 'Hello world')
+
+        # With remove_diacritics, 'cafe' should match
+        results = search('cafe')
+        self.assertEqual(len(results), 1)
+
+
+class TestSqliteSearchWithRealData(TestCase):
+    """Integration tests with realistic archived content."""
+
+    def setUp(self):
+        """Create index with realistic test data."""
+        self.temp_dir = tempfile.mkdtemp()
+        self.db_path = Path(self.temp_dir) / 'search.sqlite3'
+
+        self.settings_patch = patch(
+            'archivebox.plugins.search_backend_sqlite.search.settings'
+        )
+        self.mock_settings = self.settings_patch.start()
+        self.mock_settings.DATA_DIR = self.temp_dir
+
+        # Create index
+        conn = sqlite3.connect(str(self.db_path))
+        try:
+            conn.execute(f'''
+                CREATE VIRTUAL TABLE IF NOT EXISTS search_index
+                USING fts5(
+                    snapshot_id,
+                    url,
+                    title,
+                    content,
+                    tokenize = '{FTS_TOKENIZERS}'
+                )
+            ''')
+            # Index realistic data
+            test_data = [
+                ('snap-001', 'https://github.com/ArchiveBox/ArchiveBox',
+                 'ArchiveBox - Self-hosted web archiving',
+                 'Open source self-hosted web archiving. Collects, saves, and displays various types of content.'),
+                ('snap-002', 'https://docs.python.org/3/tutorial/',
+                 'Python 3 Tutorial',
+                 'An informal introduction to Python. Python is an easy to learn, powerful programming language.'),
+                ('snap-003', 'https://developer.mozilla.org/docs/Web/JavaScript',
+                 'JavaScript - MDN Web Docs',
+                 'JavaScript (JS) is a lightweight, interpreted programming language with first-class functions.'),
+                ('snap-004', 'https://news.ycombinator.com',
+                 'Hacker News',
+                 'Social news website focusing on computer science and entrepreneurship.'),
+                ('snap-005', 'https://en.wikipedia.org/wiki/Web_archiving',
+                 'Web archiving - Wikipedia',
+                 'Web archiving is the process of collecting portions of the World Wide Web to ensure the information is preserved.'),
+            ]
+            conn.executemany(
+                'INSERT INTO search_index (snapshot_id, url, title, content) VALUES (?, ?, ?, ?)',
+                test_data
+            )
+            conn.commit()
+        finally:
+            conn.close()
+
+    def tearDown(self):
+        """Clean up."""
+        self.settings_patch.stop()
+        import shutil
+        shutil.rmtree(self.temp_dir, ignore_errors=True)
+
+    def test_search_archivebox(self):
+        """Search for 'archivebox' should find relevant results."""
+        results = search('archivebox')
+        self.assertIn('snap-001', results)
+
+    def test_search_programming(self):
+        """Search for 'programming' should find Python and JS docs."""
+        results = search('programming')
+        self.assertIn('snap-002', results)
+        self.assertIn('snap-003', results)
+
+    def test_search_web_archiving(self):
+        """Search for 'web archiving' should find relevant results."""
+        results = search('web archiving')
+        # Both ArchiveBox and Wikipedia should match
+        self.assertIn('snap-001', results)
+        self.assertIn('snap-005', results)
+
+    def test_search_github(self):
+        """Search for 'github' should find URL match."""
+        results = search('github')
+        self.assertIn('snap-001', results)
+
+    def test_search_tutorial(self):
+        """Search for 'tutorial' should find Python tutorial."""
+        results = search('tutorial')
+        self.assertIn('snap-002', results)
+
+    def test_flush_and_search(self):
+        """Flushing a snapshot should remove it from search results."""
+        # Verify it's there first
+        results = search('archivebox')
+        self.assertIn('snap-001', results)
+
+        # Flush it
+        flush(['snap-001'])
+
+        # Should no longer be found
+        results = search('archivebox')
+        self.assertNotIn('snap-001', results)
+
+
+if __name__ == '__main__':
+    pytest.main([__file__, '-v'])
diff --git a/archivebox/workers/tests/__init__.py b/archivebox/workers/tests/__init__.py
new file mode 100644
index 00000000..f798b10f
--- /dev/null
+++ b/archivebox/workers/tests/__init__.py
@@ -0,0 +1 @@
+"""Tests for the workers module (Orchestrator, Worker, pid_utils)."""
diff --git a/archivebox/workers/tests/test_orchestrator.py b/archivebox/workers/tests/test_orchestrator.py
new file mode 100644
index 00000000..033ac087
--- /dev/null
+++ b/archivebox/workers/tests/test_orchestrator.py
@@ -0,0 +1,364 @@
+"""
+Unit tests for the Orchestrator and Worker classes.
+
+Tests cover:
+1. Orchestrator lifecycle (startup, shutdown)
+2. Queue polling and worker spawning
+3. Idle detection and exit logic
+4. Worker registration and management
+5. PID file utilities
+"""
+
+import os
+import tempfile
+import time
+import signal
+from pathlib import Path
+from unittest.mock import patch, MagicMock
+
+import pytest
+from django.test import TestCase, override_settings
+
+from archivebox.workers.pid_utils import (
+    get_pid_dir,
+    write_pid_file,
+    read_pid_file,
+    remove_pid_file,
+    is_process_alive,
+    get_all_pid_files,
+    get_all_worker_pids,
+    cleanup_stale_pid_files,
+    get_running_worker_count,
+    get_next_worker_id,
+    stop_worker,
+)
+from archivebox.workers.orchestrator import Orchestrator
+
+
+class TestPidUtils(TestCase):
+    """Test PID file utility functions."""
+
+    def setUp(self):
+        """Create a temporary directory for PID files."""
+        self.temp_dir = tempfile.mkdtemp()
+        self.pid_dir_patch = patch(
+            'archivebox.workers.pid_utils.get_pid_dir',
+            return_value=Path(self.temp_dir)
+        )
+        self.pid_dir_patch.start()
+
+    def tearDown(self):
+        """Clean up temporary directory."""
+        self.pid_dir_patch.stop()
+        import shutil
+        shutil.rmtree(self.temp_dir, ignore_errors=True)
+
+    def test_write_pid_file_orchestrator(self):
+        """write_pid_file should create orchestrator.pid for orchestrator."""
+        pid_file = write_pid_file('orchestrator')
+
+        self.assertTrue(pid_file.exists())
+        self.assertEqual(pid_file.name, 'orchestrator.pid')
+
+        content = pid_file.read_text().strip().split('\n')
+        self.assertEqual(int(content[0]), os.getpid())
+        self.assertEqual(content[1], 'orchestrator')
+
+    def test_write_pid_file_worker(self):
+        """write_pid_file should create numbered pid file for workers."""
+        pid_file = write_pid_file('snapshot', worker_id=3)
+
+        self.assertTrue(pid_file.exists())
+        self.assertEqual(pid_file.name, 'snapshot_worker_3.pid')
+
+    def test_write_pid_file_with_extractor(self):
+        """write_pid_file should include extractor in content."""
+        pid_file = write_pid_file('archiveresult', worker_id=0, extractor='singlefile')
+
+        content = pid_file.read_text().strip().split('\n')
+        self.assertEqual(content[2], 'singlefile')
+
+    def test_read_pid_file_valid(self):
+        """read_pid_file should parse valid PID files."""
+        pid_file = write_pid_file('snapshot', worker_id=1)
+        info = read_pid_file(pid_file)
+
+        self.assertIsNotNone(info)
+        self.assertEqual(info['pid'], os.getpid())
+        self.assertEqual(info['worker_type'], 'snapshot')
+        self.assertEqual(info['pid_file'], pid_file)
+        self.assertIsNotNone(info['started_at'])
+
+    def test_read_pid_file_invalid(self):
+        """read_pid_file should return None for invalid files."""
+        invalid_file = Path(self.temp_dir) / 'invalid.pid'
+        invalid_file.write_text('not valid')
+
+        info = read_pid_file(invalid_file)
+        self.assertIsNone(info)
+
+    def test_read_pid_file_nonexistent(self):
+        """read_pid_file should return None for nonexistent files."""
+        info = read_pid_file(Path(self.temp_dir) / 'nonexistent.pid')
+        self.assertIsNone(info)
+
+    def test_remove_pid_file(self):
+        """remove_pid_file should delete the file."""
+        pid_file = write_pid_file('test', worker_id=0)
+        self.assertTrue(pid_file.exists())
+
+        remove_pid_file(pid_file)
+        self.assertFalse(pid_file.exists())
+
+    def test_remove_pid_file_nonexistent(self):
+        """remove_pid_file should not raise for nonexistent files."""
+        # Should not raise
+        remove_pid_file(Path(self.temp_dir) / 'nonexistent.pid')
+
+    def test_is_process_alive_current(self):
+        """is_process_alive should return True for current process."""
+        self.assertTrue(is_process_alive(os.getpid()))
+
+    def test_is_process_alive_dead(self):
+        """is_process_alive should return False for dead processes."""
+        # PID 999999 is unlikely to exist
+        self.assertFalse(is_process_alive(999999))
+
+    def test_get_all_pid_files(self):
+        """get_all_pid_files should return all .pid files."""
+        write_pid_file('orchestrator')
+        write_pid_file('snapshot', worker_id=0)
+        write_pid_file('crawl', worker_id=1)
+
+        files = get_all_pid_files()
+        self.assertEqual(len(files), 3)
+
+    def test_get_all_worker_pids(self):
+        """get_all_worker_pids should return info for live workers."""
+        write_pid_file('snapshot', worker_id=0)
+        write_pid_file('crawl', worker_id=1)
+
+        workers = get_all_worker_pids()
+        # All should be alive since they're current process PID
+        self.assertEqual(len(workers), 2)
+
+    def test_get_all_worker_pids_filtered(self):
+        """get_all_worker_pids should filter by worker type."""
+        write_pid_file('snapshot', worker_id=0)
+        write_pid_file('snapshot', worker_id=1)
+        write_pid_file('crawl', worker_id=0)
+
+        snapshot_workers = get_all_worker_pids('snapshot')
+        self.assertEqual(len(snapshot_workers), 2)
+
+        crawl_workers = get_all_worker_pids('crawl')
+        self.assertEqual(len(crawl_workers), 1)
+
+    def test_cleanup_stale_pid_files(self):
+        """cleanup_stale_pid_files should remove files for dead processes."""
+        # Create a PID file with a dead PID
+        stale_file = Path(self.temp_dir) / 'stale_worker_0.pid'
+        stale_file.write_text('999999\nstale\n\n2024-01-01T00:00:00+00:00\n')
+
+        # Create a valid PID file (current process)
+        write_pid_file('valid', worker_id=0)
+
+        removed = cleanup_stale_pid_files()
+
+        self.assertEqual(removed, 1)
+        self.assertFalse(stale_file.exists())
+
+    def test_get_running_worker_count(self):
+        """get_running_worker_count should count workers of a type."""
+        write_pid_file('snapshot', worker_id=0)
+        write_pid_file('snapshot', worker_id=1)
+        write_pid_file('crawl', worker_id=0)
+
+        self.assertEqual(get_running_worker_count('snapshot'), 2)
+        self.assertEqual(get_running_worker_count('crawl'), 1)
+        self.assertEqual(get_running_worker_count('archiveresult'), 0)
+
+    def test_get_next_worker_id(self):
+        """get_next_worker_id should find lowest unused ID."""
+        write_pid_file('snapshot', worker_id=0)
+        write_pid_file('snapshot', worker_id=1)
+        write_pid_file('snapshot', worker_id=3)  # Skip 2
+
+        next_id = get_next_worker_id('snapshot')
+        self.assertEqual(next_id, 2)
+
+    def test_get_next_worker_id_empty(self):
+        """get_next_worker_id should return 0 if no workers exist."""
+        next_id = get_next_worker_id('snapshot')
+        self.assertEqual(next_id, 0)
+
+
+class TestOrchestratorUnit(TestCase):
+    """Unit tests for Orchestrator class (mocked dependencies)."""
+
+    def test_orchestrator_creation(self):
+        """Orchestrator should initialize with correct defaults."""
+        orchestrator = Orchestrator(exit_on_idle=True)
+
+        self.assertTrue(orchestrator.exit_on_idle)
+        self.assertEqual(orchestrator.idle_count, 0)
+        self.assertIsNone(orchestrator.pid_file)
+
+    def test_orchestrator_repr(self):
+        """Orchestrator __repr__ should include PID."""
+        orchestrator = Orchestrator()
+        repr_str = repr(orchestrator)
+
+        self.assertIn('Orchestrator', repr_str)
+        self.assertIn(str(os.getpid()), repr_str)
+
+    def test_has_pending_work(self):
+        """has_pending_work should check if any queue has items."""
+        orchestrator = Orchestrator()
+
+        self.assertFalse(orchestrator.has_pending_work({'crawl': 0, 'snapshot': 0}))
+        self.assertTrue(orchestrator.has_pending_work({'crawl': 0, 'snapshot': 5}))
+        self.assertTrue(orchestrator.has_pending_work({'crawl': 10, 'snapshot': 0}))
+
+    def test_should_exit_not_exit_on_idle(self):
+        """should_exit should return False when exit_on_idle is False."""
+        orchestrator = Orchestrator(exit_on_idle=False)
+        orchestrator.idle_count = 100
+
+        self.assertFalse(orchestrator.should_exit({'crawl': 0}))
+
+    def test_should_exit_pending_work(self):
+        """should_exit should return False when there's pending work."""
+        orchestrator = Orchestrator(exit_on_idle=True)
+        orchestrator.idle_count = 100
+
+        self.assertFalse(orchestrator.should_exit({'crawl': 5}))
+
+    @patch.object(Orchestrator, 'has_running_workers')
+    def test_should_exit_running_workers(self, mock_has_workers):
+        """should_exit should return False when workers are running."""
+        mock_has_workers.return_value = True
+        orchestrator = Orchestrator(exit_on_idle=True)
+        orchestrator.idle_count = 100
+
+        self.assertFalse(orchestrator.should_exit({'crawl': 0}))
+
+    @patch.object(Orchestrator, 'has_running_workers')
+    @patch.object(Orchestrator, 'has_future_work')
+    def test_should_exit_idle_timeout(self, mock_future, mock_workers):
+        """should_exit should return True after idle timeout with no work."""
+        mock_workers.return_value = False
+        mock_future.return_value = False
+
+        orchestrator = Orchestrator(exit_on_idle=True)
+        orchestrator.idle_count = orchestrator.IDLE_TIMEOUT
+
+        self.assertTrue(orchestrator.should_exit({'crawl': 0, 'snapshot': 0}))
+
+    @patch.object(Orchestrator, 'has_running_workers')
+    @patch.object(Orchestrator, 'has_future_work')
+    def test_should_exit_below_idle_timeout(self, mock_future, mock_workers):
+        """should_exit should return False below idle timeout."""
+        mock_workers.return_value = False
+        mock_future.return_value = False
+
+        orchestrator = Orchestrator(exit_on_idle=True)
+        orchestrator.idle_count = orchestrator.IDLE_TIMEOUT - 1
+
+        self.assertFalse(orchestrator.should_exit({'crawl': 0}))
+
+    def test_should_spawn_worker_no_queue(self):
+        """should_spawn_worker should return False when queue is empty."""
+        orchestrator = Orchestrator()
+
+        # Create a mock worker class
+        mock_worker = MagicMock()
+        mock_worker.get_running_workers.return_value = []
+
+        self.assertFalse(orchestrator.should_spawn_worker(mock_worker, 0))
+
+    def test_should_spawn_worker_at_limit(self):
+        """should_spawn_worker should return False when at per-type limit."""
+        orchestrator = Orchestrator()
+
+        mock_worker = MagicMock()
+        mock_worker.get_running_workers.return_value = [{}] * orchestrator.MAX_WORKERS_PER_TYPE
+
+        self.assertFalse(orchestrator.should_spawn_worker(mock_worker, 10))
+
+    @patch.object(Orchestrator, 'get_total_worker_count')
+    def test_should_spawn_worker_at_total_limit(self, mock_total):
+        """should_spawn_worker should return False when at total limit."""
+        orchestrator = Orchestrator()
+        mock_total.return_value = orchestrator.MAX_TOTAL_WORKERS
+
+        mock_worker = MagicMock()
+        mock_worker.get_running_workers.return_value = []
+
+        self.assertFalse(orchestrator.should_spawn_worker(mock_worker, 10))
+
+    @patch.object(Orchestrator, 'get_total_worker_count')
+    def test_should_spawn_worker_success(self, mock_total):
+        """should_spawn_worker should return True when conditions are met."""
+        orchestrator = Orchestrator()
+        mock_total.return_value = 0
+
+        mock_worker = MagicMock()
+        mock_worker.get_running_workers.return_value = []
+        mock_worker.MAX_CONCURRENT_TASKS = 5
+
+        self.assertTrue(orchestrator.should_spawn_worker(mock_worker, 10))
+
+    @patch.object(Orchestrator, 'get_total_worker_count')
+    def test_should_spawn_worker_enough_workers(self, mock_total):
+        """should_spawn_worker should return False when enough workers for queue."""
+        orchestrator = Orchestrator()
+        mock_total.return_value = 2
+
+        mock_worker = MagicMock()
+        mock_worker.get_running_workers.return_value = [{}]  # 1 worker running
+        mock_worker.MAX_CONCURRENT_TASKS = 5  # Can handle 5 items
+
+        # Queue size (3) <= running_workers (1) * MAX_CONCURRENT_TASKS (5)
+        self.assertFalse(orchestrator.should_spawn_worker(mock_worker, 3))
+
+
+class TestOrchestratorIsRunning(TestCase):
+    """Test Orchestrator.is_running() class method."""
+
+    def setUp(self):
+        """Create a temporary directory for PID files."""
+        self.temp_dir = tempfile.mkdtemp()
+        self.pid_dir_patch = patch(
+            'archivebox.workers.pid_utils.get_pid_dir',
+            return_value=Path(self.temp_dir)
+        )
+        self.pid_dir_patch.start()
+
+    def tearDown(self):
+        """Clean up."""
+        self.pid_dir_patch.stop()
+        import shutil
+        shutil.rmtree(self.temp_dir, ignore_errors=True)
+
+    def test_is_running_no_pid_file(self):
+        """is_running should return False when no orchestrator PID file."""
+        self.assertFalse(Orchestrator.is_running())
+
+    def test_is_running_with_live_orchestrator(self):
+        """is_running should return True when orchestrator PID file exists."""
+        write_pid_file('orchestrator')
+        self.assertTrue(Orchestrator.is_running())
+
+    def test_is_running_with_dead_orchestrator(self):
+        """is_running should return False when orchestrator process is dead."""
+        # Create a PID file with a dead PID
+        pid_file = Path(self.temp_dir) / 'orchestrator.pid'
+        pid_file.write_text('999999\norchestrator\n\n2024-01-01T00:00:00+00:00\n')
+
+        # The get_all_worker_pids filters out dead processes
+        self.assertFalse(Orchestrator.is_running())
+
+
+if __name__ == '__main__':
+    pytest.main([__file__, '-v'])