diff --git a/tests/test_monitor.py b/tests/test_monitor.py
new file mode 100644
index 0000000..4cc386a
--- /dev/null
+++ b/tests/test_monitor.py
@@ -0,0 +1,165 @@
+"""Tests for DevTrace monitor module."""
+
+import pytest
+import tempfile
+from pathlib import Path
+from unittest.mock import Mock, patch, MagicMock
+
+from src.storage.database import Database
+from src.monitor.filesystem import FileSystemMonitor, FileEventHandler
+from src.monitor.commands import CommandCapture
+from src.monitor.git import GitTracker
+
+
+@pytest.fixture
+def temp_db():
+    """Create a temporary database for testing."""
+    with tempfile.NamedTemporaryFile(suffix=".db", delete=False) as f:
+        db_path = Path(f.name)
+
+    db = Database(db_path)
+    db.initialize()
+
+    yield db
+
+    db.close()
+    db_path.unlink(missing_ok=True)
+
+
+@pytest.fixture
+def temp_dir():
+    """Create a temporary directory for testing."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        yield Path(tmpdir)
+
+
+class TestFileSystemMonitor:
+    """Tests for FileSystemMonitor."""
+
+    def test_monitor_creation(self, temp_db):
+        """Test monitor creation."""
+        session_id = temp_db.create_session("Test", "/tmp").id
+        monitor = FileSystemMonitor(temp_db, session_id)
+
+        assert monitor.session_id == session_id
+        assert monitor.observer is None
+
+    def test_event_handler_should_watch(self, temp_db):
+        """Test event handler path filtering."""
+        session_id = temp_db.create_session("Test", "/tmp").id
+        handler = FileEventHandler(temp_db, session_id)
+
+        assert handler._should_watch("/project/main.py") is True
+        assert handler._should_watch("/project/src/app.js") is True
+        assert handler._should_watch("/project/README.md") is True
+
+    def test_event_handler_ignores_ignored_patterns(self, temp_db):
+        """Test event handler ignores specified patterns."""
+        session_id = temp_db.create_session("Test", "/tmp").id
+        handler = FileEventHandler(
+            temp_db,
+            session_id,
+            ignored_patterns={"__pycache__", ".git"}
+        )
+
+        assert handler._should_watch("/project/__pycache__/cache.py") is False
+        assert handler._should_watch("/project/.git/config") is False
+        assert handler._should_watch("/project/src/main.py") is True
+
+    def test_compute_content_hash(self, temp_db, temp_dir):
+        """Test content hash computation."""
+        session_id = temp_db.create_session("Test", str(temp_dir)).id
+        handler = FileEventHandler(temp_db, session_id)
+
+        test_file = temp_dir / "test.py"
+        test_file.write_text("print('hello')")
+
+        hash1 = handler._compute_content_hash(str(test_file))
+        hash2 = handler._compute_content_hash(str(test_file))
+
+        assert hash1 is not None
+        assert hash1 == hash2
+
+        test_file.write_text("print('world')")
+        hash3 = handler._compute_content_hash(str(test_file))
+
+        assert hash1 != hash3
+
+
+class TestCommandCapture:
+    """Tests for CommandCapture."""
+
+    def test_capture_creation(self, temp_db):
+        """Test capture creation."""
+        session_id = temp_db.create_session("Test", "/tmp").id
+        capture = CommandCapture(temp_db, session_id)
+
+        assert capture.session_id == session_id
+
+    @patch('builtins.open', side_effect=FileNotFoundError)
+    def test_capture_handles_missing_history(self, temp_db):
+        """Test capture handles missing history file."""
+        session_id = temp_db.create_session("Test", "/tmp").id
+        capture = CommandCapture(temp_db, session_id)
+
+        result = capture.capture_new_commands()
+
+        assert result == []
+
+    def test_capture_command(self, temp_db):
+        """Test direct command capture."""
+        session_id = temp_db.create_session("Test", "/tmp").id
+        capture = CommandCapture(temp_db, session_id)
+
+        event_id = capture.capture_command("ls -la", exit_code=0)
+
+        assert event_id is not None
+
+
+class TestGitTracker:
+    """Tests for GitTracker."""
+
+    def test_tracker_creation(self, temp_db):
+        """Test tracker creation."""
+        session_id = temp_db.create_session("Test", "/tmp").id
+        tracker = GitTracker(temp_db, session_id)
+
+        assert tracker.session_id == session_id
+
+    @patch('subprocess.run')
+    def test_get_current_branch(self, mock_run, temp_db, temp_dir):
+        """Test getting current branch."""
+        mock_run.return_value.stdout = "main\n"
+        mock_run.return_value.returncode = 0
+
+        session_id = temp_db.create_session("Test", str(temp_dir)).id
+        tracker = GitTracker(temp_db, session_id)
+
+        branch = tracker._get_current_branch(str(temp_dir))
+
+        assert branch == "main"
+
+    @patch('subprocess.run')
+    def test_get_current_commit(self, mock_run, temp_db, temp_dir):
+        """Test getting current commit."""
+        mock_run.return_value.stdout = "abc123def456\n"
+        mock_run.return_value.returncode = 0
+
+        session_id = temp_db.create_session("Test", str(temp_dir)).id
+        tracker = GitTracker(temp_db, session_id)
+
+        commit = tracker._get_current_commit(str(temp_dir))
+
+        assert commit == "abc123def456"
+
+    @patch('subprocess.run')
+    def test_get_current_commit_not_git_repo(self, mock_run, temp_db, temp_dir):
+        """Test getting commit when not in git repo."""
+        mock_run.return_value.returncode = 128
+
+        session_id = temp_db.create_session("Test", str(temp_dir)).id
+        tracker = GitTracker(temp_db, session_id)
+
+        commit = tracker._get_current_commit(str(temp_dir))
+
+        assert commit is None