diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 52142c2..50f628b 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -7,9 +7,8 @@ on:
     branches: [main]
 
 jobs:
-  test:
+  unit-test:
     runs-on: ubuntu-latest
-
     steps:
       - uses: actions/checkout@v4
 
@@ -19,13 +18,27 @@ jobs:
           python-version: "3.11"
 
       - name: Install dependencies
-        run: |
-          pip install anthropic python-dotenv openai
+        run: pip install anthropic python-dotenv
 
-      - name: Run tests
+      - name: Run unit tests
+        run: python tests/test_unit.py
+
+  integration-test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+
+      - name: Install dependencies
+        run: pip install anthropic python-dotenv openai
+
+      - name: Run integration tests
         env:
           TEST_API_KEY: ${{ secrets.TEST_API_KEY }}
           TEST_BASE_URL: ${{ secrets.TEST_BASE_URL }}
           TEST_MODEL: ${{ secrets.TEST_MODEL }}
-        run: |
-          python tests/test_agent.py
+        run: python tests/test_agent.py
diff --git a/tests/test_unit.py b/tests/test_unit.py
new file mode 100644
index 0000000..a6b201b
--- /dev/null
+++ b/tests/test_unit.py
@@ -0,0 +1,245 @@
+"""
+Unit tests for learn-claude-code agents.
+
+These tests don't require API calls - they verify code structure and logic.
+"""
+import os
+import sys
+import importlib.util
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+
+# =============================================================================
+# Import Tests
+# =============================================================================
+
+def test_imports():
+    """Test that all agent modules can be imported."""
+    agents = [
+        "v0_bash_agent",
+        "v0_bash_agent_mini",
+        "v1_basic_agent",
+        "v2_todo_agent",
+        "v3_subagent",
+        "v4_skills_agent"
+    ]
+
+    for agent in agents:
+        spec = importlib.util.find_spec(agent)
+        assert spec is not None, f"Failed to find {agent}"
+        print(f"  Found: {agent}")
+
+    print("PASS: test_imports")
+    return True
+
+
+# =============================================================================
+# TodoManager Tests
+# =============================================================================
+
+def test_todo_manager_basic():
+    """Test TodoManager basic operations."""
+    from v2_todo_agent import TodoManager
+
+    tm = TodoManager()
+
+    # Test valid update
+    result = tm.update([
+        {"content": "Task 1", "status": "pending", "activeForm": "Doing task 1"},
+        {"content": "Task 2", "status": "in_progress", "activeForm": "Doing task 2"},
+    ])
+
+    assert "Task 1" in result
+    assert "Task 2" in result
+    assert len(tm.items) == 2
+
+    print("PASS: test_todo_manager_basic")
+    return True
+
+
+def test_todo_manager_constraints():
+    """Test TodoManager enforces constraints."""
+    from v2_todo_agent import TodoManager
+
+    tm = TodoManager()
+
+    # Test: only one in_progress allowed (should raise or return error)
+    try:
+        result = tm.update([
+            {"content": "Task 1", "status": "in_progress", "activeForm": "Doing 1"},
+            {"content": "Task 2", "status": "in_progress", "activeForm": "Doing 2"},
+        ])
+        # If no exception, check result contains error
+        assert "Error" in result or "error" in result.lower()
+    except ValueError as e:
+        # Exception is expected - constraint enforced
+        assert "in_progress" in str(e).lower()
+
+    # Test: max 20 items
+    tm2 = TodoManager()
+    many_items = [{"content": f"Task {i}", "status": "pending", "activeForm": f"Doing {i}"} for i in range(25)]
+    try:
+        tm2.update(many_items)
+    except ValueError:
+        pass  # Exception is fine
+    assert len(tm2.items) <= 20
+
+    print("PASS: test_todo_manager_constraints")
+    return True
+
+
+# =============================================================================
+# Reminder Tests
+# =============================================================================
+
+def test_reminder_constants():
+    """Test reminder constants are defined correctly."""
+    from v2_todo_agent import INITIAL_REMINDER, NAG_REMINDER
+
+    assert "<reminder>" in INITIAL_REMINDER
+    assert "</reminder>" in INITIAL_REMINDER
+    assert "<reminder>" in NAG_REMINDER
+    assert "</reminder>" in NAG_REMINDER
+    assert "todo" in NAG_REMINDER.lower() or "Todo" in NAG_REMINDER
+
+    print("PASS: test_reminder_constants")
+    return True
+
+
+def test_nag_reminder_in_agent_loop():
+    """Test NAG_REMINDER injection is inside agent_loop."""
+    import inspect
+    from v2_todo_agent import agent_loop, NAG_REMINDER
+
+    source = inspect.getsource(agent_loop)
+
+    # NAG_REMINDER should be referenced in agent_loop
+    assert "NAG_REMINDER" in source, "NAG_REMINDER should be in agent_loop"
+    assert "rounds_without_todo" in source, "rounds_without_todo check should be in agent_loop"
+    assert "results.insert" in source or "results.append" in source, "Should inject into results"
+
+    print("PASS: test_nag_reminder_in_agent_loop")
+    return True
+
+
+# =============================================================================
+# Configuration Tests
+# =============================================================================
+
+def test_env_config():
+    """Test environment variable configuration."""
+    # Save original values
+    orig_model = os.environ.get("MODEL_ID")
+    orig_base = os.environ.get("ANTHROPIC_BASE_URL")
+
+    try:
+        # Set test values
+        os.environ["MODEL_ID"] = "test-model-123"
+        os.environ["ANTHROPIC_BASE_URL"] = "https://test.example.com"
+
+        # Re-import to pick up new env vars
+        import importlib
+        import v1_basic_agent
+        importlib.reload(v1_basic_agent)
+
+        assert v1_basic_agent.MODEL == "test-model-123", f"MODEL should be test-model-123, got {v1_basic_agent.MODEL}"
+
+        print("PASS: test_env_config")
+        return True
+
+    finally:
+        # Restore original values
+        if orig_model:
+            os.environ["MODEL_ID"] = orig_model
+        else:
+            os.environ.pop("MODEL_ID", None)
+        if orig_base:
+            os.environ["ANTHROPIC_BASE_URL"] = orig_base
+        else:
+            os.environ.pop("ANTHROPIC_BASE_URL", None)
+
+
+def test_default_model():
+    """Test default model when env var not set."""
+    orig = os.environ.pop("MODEL_ID", None)
+
+    try:
+        import importlib
+        import v1_basic_agent
+        importlib.reload(v1_basic_agent)
+
+        assert "claude" in v1_basic_agent.MODEL.lower(), f"Default model should contain 'claude': {v1_basic_agent.MODEL}"
+
+        print("PASS: test_default_model")
+        return True
+
+    finally:
+        if orig:
+            os.environ["MODEL_ID"] = orig
+
+
+# =============================================================================
+# Tool Schema Tests
+# =============================================================================
+
+def test_tool_schemas():
+    """Test tool schemas are valid."""
+    from v1_basic_agent import TOOLS
+
+    required_tools = {"bash", "read_file", "write_file", "edit_file"}
+    tool_names = {t["name"] for t in TOOLS}
+
+    assert required_tools.issubset(tool_names), f"Missing tools: {required_tools - tool_names}"
+
+    for tool in TOOLS:
+        assert "name" in tool
+        assert "description" in tool
+        assert "input_schema" in tool
+        assert tool["input_schema"].get("type") == "object"
+
+    print("PASS: test_tool_schemas")
+    return True
+
+
+# =============================================================================
+# Main
+# =============================================================================
+
+if __name__ == "__main__":
+    tests = [
+        test_imports,
+        test_todo_manager_basic,
+        test_todo_manager_constraints,
+        test_reminder_constants,
+        test_nag_reminder_in_agent_loop,
+        test_env_config,
+        test_default_model,
+        test_tool_schemas,
+    ]
+
+    failed = []
+    for test_fn in tests:
+        name = test_fn.__name__
+        print(f"\n{'='*50}")
+        print(f"Running: {name}")
+        print('='*50)
+        try:
+            if not test_fn():
+                failed.append(name)
+        except Exception as e:
+            print(f"FAILED: {e}")
+            import traceback
+            traceback.print_exc()
+            failed.append(name)
+
+    print(f"\n{'='*50}")
+    print(f"Results: {len(tests) - len(failed)}/{len(tests)} passed")
+    print('='*50)
+
+    if failed:
+        print(f"FAILED: {failed}")
+        sys.exit(1)
+    else:
+        print("All unit tests passed!")
+        sys.exit(0)