diff --git a/tests/test_egg.py b/tests/test_egg.py
new file mode 100644
index 0000000..969e385
--- /dev/null
+++ b/tests/test_egg.py
@@ -0,0 +1,176 @@
+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.egg 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_egg_symmetry_ab_to_ba(temp_db):
+    """Test symmetry: given fact a=b and idea b=a, egg should produce fact b=a."""
+    addr, engine, session = temp_db
+
+    # Add fact a=b
+    async with session() as sess:
+        sess.add(Facts(data="----\n(binary == a b)\n"))
+        sess.add(Ideas(data="----\n(binary == b a)\n"))
+        await sess.commit()
+
+    # Run the main function with a timeout
+    task = asyncio.create_task(main(addr, engine, session))
+    await asyncio.sleep(0.3)
+    task.cancel()
+    try:
+        await task
+    except asyncio.CancelledError:
+        pass
+
+    # Verify that fact b=a was produced
+    async with session() as sess:
+        facts = await sess.scalars(select(Facts))
+        fact_data = [f.data for f in facts.all()]
+        assert "----\n(binary == b a)\n" in fact_data
+
+
+@pytest.mark.asyncio
+async def test_egg_transitivity_abc(temp_db):
+    """Test transitivity: given a=b, b=c, and idea a=c, egg should produce a=c."""
+    addr, engine, session = temp_db
+
+    # Add facts a=b and b=c
+    async with session() as sess:
+        sess.add(Facts(data="----\n(binary == a b)\n"))
+        sess.add(Facts(data="----\n(binary == b c)\n"))
+        sess.add(Ideas(data="----\n(binary == a c)\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
+
+    # Verify that fact a=c was produced
+    async with session() as sess:
+        facts = await sess.scalars(select(Facts))
+        fact_data = [f.data for f in facts.all()]
+        assert "----\n(binary == a c)\n" in fact_data
+
+
+@pytest.mark.asyncio
+async def test_egg_congruence_fx_fy(temp_db):
+    """Test congruence: given x=y, expect f(x)=f(y), egg should produce it."""
+    addr, engine, session = temp_db
+
+    # Add fact x=y and idea f(x)=f(y)
+    async with session() as sess:
+        sess.add(Facts(data="----\n(binary == x y)\n"))
+        sess.add(Ideas(data="----\n(binary == (unary f x) (unary f y))\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
+
+    # Verify that fact f(x)=f(y) was produced
+    async with session() as sess:
+        facts = await sess.scalars(select(Facts))
+        fact_data = [f.data for f in facts.all()]
+        assert "----\n(binary == (unary f x) (unary f y))\n" in fact_data
+
+
+@pytest.mark.asyncio
+async def test_egg_substitution_fx_with_xy(temp_db):
+    """Test substitution: given f(x) and x=y, expect f(y) can be satisfied."""
+    addr, engine, session = temp_db
+
+    # Add fact f(x) and x=y, then idea f(y)
+    async with session() as sess:
+        sess.add(Facts(data="----\n(unary f x)\n"))
+        sess.add(Facts(data="----\n(binary == x y)\n"))
+        sess.add(Ideas(data="----\n(unary f y)\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
+
+    # Verify that the idea was satisfied (removed from pool or fact produced)
+    async with session() as sess:
+        facts = await sess.scalars(select(Facts))
+        fact_data = [f.data for f in facts.all()]
+        # The idea should be satisfied because f(x) and x=y implies f(y)
+        assert "----\n(unary f y)\n" in fact_data
+
+
+@pytest.mark.asyncio
+async def test_egg_substitution_fx_xyz(temp_db):
+    """Test substitution chain: given x=y, y=z, f(x), expect f(z) can be satisfied."""
+    addr, engine, session = temp_db
+
+    # Add facts x=y, y=z, f(x), then idea f(z)
+    async with session() as sess:
+        sess.add(Facts(data="----\n(binary == x y)\n"))
+        sess.add(Facts(data="----\n(binary == y z)\n"))
+        sess.add(Facts(data="----\n(unary f x)\n"))
+        sess.add(Ideas(data="----\n(unary f z)\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
+
+    # Verify that f(z) was produced
+    async with session() as sess:
+        facts = await sess.scalars(select(Facts))
+        fact_data = [f.data for f in facts.all()]
+        assert "----\n(unary f z)\n" in fact_data
+
+
+@pytest.mark.asyncio
+async def test_egg_cancellation(temp_db):
+    """Test that the egg 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)
+    task.cancel()
+
+    # Should complete without hanging
+    try:
+        await task
+    except asyncio.CancelledError:
+        pass