diff --git a/tests/test_ds.py b/tests/test_ds.py
new file mode 100644
index 0000000..34fefe4
--- /dev/null
+++ b/tests/test_ds.py
@@ -0,0 +1,190 @@
+import asyncio
+import tempfile
+import pathlib
+import pytest
+import pytest_asyncio
+from sqlalchemy import select
+from ddss.orm import initialize_database, Facts, Ideas
+from ddss.ds import main
+
+
+@pytest_asyncio.fixture
+async def temp_db():
+    """Fixture to create a temporary database."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        db_path = pathlib.Path(tmpdir) / "test.db"
+        addr = f"sqlite+aiosqlite:///{db_path.as_posix()}"
+        engine, session = await initialize_database(addr)
+        yield addr, engine, session
+        await engine.dispose()
+
+
+@pytest.mark.asyncio
+async def test_ds_simple_modus_ponens(temp_db):
+    """Test simple modus ponens: 'a => b' with '=> a' produces '=> b'."""
+    addr, engine, session = temp_db
+
+    # Add initial facts: a => b and => a
+    async with session() as sess:
+        sess.add(Facts(data="a\n----\nb\n"))
+        sess.add(Facts(data="----\na\n"))
+        await sess.commit()
+
+    # Run the main function with a timeout
+    task = asyncio.create_task(main(addr, engine, session))
+    await asyncio.sleep(0.3)  # Give it time to process
+    task.cancel()
+    try:
+        await task
+    except asyncio.CancelledError:
+        pass
+
+    # Check that the new fact '=> b' was created
+    async with session() as sess:
+        all_facts = await sess.scalars(select(Facts))
+        facts_data = [f.data for f in all_facts]
+
+    assert "----\nb\n" in facts_data
+
+
+@pytest.mark.asyncio
+async def test_ds_multi_premise_with_idea(temp_db):
+    """Test multi-premise rule: 'a, b => c' with '=> a' produces 'b => c' and idea '=> b'."""
+    addr, engine, session = temp_db
+
+    # Add initial facts: a, b => c and => a
+    async with session() as sess:
+        sess.add(Facts(data="a\nb\n----\nc\n"))
+        sess.add(Facts(data="----\na\n"))
+        await sess.commit()
+
+    # Run the main function with a timeout
+    task = asyncio.create_task(main(addr, engine, session))
+    await asyncio.sleep(0.3)  # Give it time to process
+    task.cancel()
+    try:
+        await task
+    except asyncio.CancelledError:
+        pass
+
+    # Check that the new fact 'b => c' was created
+    async with session() as sess:
+        all_facts = await sess.scalars(select(Facts))
+        facts_data = [f.data for f in all_facts]
+
+    assert "b\n----\nc\n" in facts_data
+
+    # Check that the idea '=> b' was created
+    async with session() as sess:
+        all_ideas = await sess.scalars(select(Ideas))
+        ideas_data = [i.data for i in all_ideas]
+
+    assert "----\nb\n" in ideas_data
+
+
+@pytest.mark.asyncio
+async def test_ds_no_inference_without_matching_facts(temp_db):
+    """Test that no inference occurs when facts don't match."""
+    addr, engine, session = temp_db
+
+    # Add facts that don't match: a => b and => c
+    async with session() as sess:
+        sess.add(Facts(data="a\n----\nb\n"))
+        sess.add(Facts(data="----\nc\n"))
+        await sess.commit()
+
+    # Run the main function with a timeout
+    task = asyncio.create_task(main(addr, engine, session))
+    await asyncio.sleep(0.3)  # Give it time to process
+    task.cancel()
+    try:
+        await task
+    except asyncio.CancelledError:
+        pass
+
+    # Check that only the original facts exist (no new inference)
+    async with session() as sess:
+        all_facts = await sess.scalars(select(Facts))
+        facts_data = [f.data for f in all_facts]
+
+    # Should only have the original 2 facts
+    assert len(facts_data) == 2
+    assert "a\n----\nb\n" in facts_data
+    assert "----\nc\n" in facts_data
+
+
+@pytest.mark.asyncio
+async def test_ds_multiple_inferences(temp_db):
+    """Test multiple inference steps in sequence."""
+    addr, engine, session = temp_db
+
+    # Add facts for chained inference: a => b, b => c, => a
+    async with session() as sess:
+        sess.add(Facts(data="a\n----\nb\n"))
+        sess.add(Facts(data="b\n----\nc\n"))
+        sess.add(Facts(data="----\na\n"))
+        await sess.commit()
+
+    # Run the main function with a timeout
+    task = asyncio.create_task(main(addr, engine, session))
+    await asyncio.sleep(0.5)  # Give it time for multiple rounds
+    task.cancel()
+    try:
+        await task
+    except asyncio.CancelledError:
+        pass
+
+    # Check that both => b and => c were inferred
+    async with session() as sess:
+        all_facts = await sess.scalars(select(Facts))
+        facts_data = [f.data for f in all_facts]
+
+    assert "----\nb\n" in facts_data
+    assert "----\nc\n" in facts_data
+
+
+@pytest.mark.asyncio
+async def test_ds_cancellation(temp_db):
+    """Test that the ds main function can be cancelled without hanging."""
+    addr, engine, session = temp_db
+
+    # Run the main function and cancel it
+    task = asyncio.create_task(main(addr, engine, session))
+    await asyncio.sleep(0.1)  # Let it start
+    task.cancel()
+
+    # Should complete without hanging
+    try:
+        await task
+    except asyncio.CancelledError:
+        pass  # Expected - cancellation worked
+
+
+@pytest.mark.asyncio
+async def test_ds_duplicate_facts_not_added(temp_db):
+    """Test that duplicate facts are not added to the database."""
+    addr, engine, session = temp_db
+
+    # Add facts that will produce a duplicate: a => b twice with => a
+    async with session() as sess:
+        sess.add(Facts(data="a\n----\nb\n"))
+        sess.add(Facts(data="----\na\n"))
+        await sess.commit()
+
+    # Run the main function
+    task = asyncio.create_task(main(addr, engine, session))
+    await asyncio.sleep(0.3)
+    task.cancel()
+    try:
+        await task
+    except asyncio.CancelledError:
+        pass
+
+    # Count the facts - should have 3: original 2 + 1 inferred => b
+    async with session() as sess:
+        all_facts = await sess.scalars(select(Facts))
+        facts_list = list(all_facts)
+
+    assert len(facts_list) == 3
+    facts_data = [f.data for f in facts_list]
+    assert facts_data.count("----\nb\n") == 1  # Should only appear once