Test Suite Review

pyproject.toml

@@ -148,6 +148,9 @@
             "-W ignore::beartype.roar.BeartypeDecorHintPep585DeprecationWarning",
         ]
         doctest_optionflags="NORMALIZE_WHITESPACE ELLIPSIS FLOAT_CMP"
+        markers=[
+            "slow: marks tests as slow (deselect with '-m \"not slow\"')",
+        ]
         filterwarnings=[
             "ignore:pkg_resources is deprecated as an API:DeprecationWarning",
             # Ignore numpy.distutils deprecation warning caused by pandas

tests/acceptance/model_bridge/compatibility/test_activation_cache.py

@@ -4,7 +4,6 @@
 import torch
 
 from transformer_lens.ActivationCache import ActivationCache
-from transformer_lens.model_bridge import TransformerBridge
 
 
 class TestActivationCacheCompatibility:
@@ -14,16 +13,15 @@ class TestActivationCacheCompatibility:
     def cleanup_after_class(self):
         """Clean up memory after each test class."""
         yield
-        # Clear GPU memory
         if torch.cuda.is_available():
             torch.cuda.empty_cache()
         for _ in range(3):
             gc.collect()
 
     @pytest.fixture(scope="class")
-    def bridge_model(self):
-        """Create a TransformerBridge model for testing."""
-        return TransformerBridge.boot_transformers("gpt2", device="cpu")
+    def bridge_model(self, gpt2_bridge):
+        """Use session-scoped gpt2 bridge."""
+        return gpt2_bridge
 
     @pytest.fixture(scope="class")
     def sample_cache(self, bridge_model):

tests/acceptance/model_bridge/compatibility/test_backward_hooks.py

@@ -4,27 +4,23 @@
 import pytest
 import torch
 
-from transformer_lens import HookedTransformer
-from transformer_lens.model_bridge import TransformerBridge
-
 
 class TestBackwardHookCompatibility:
     """Test backward hook compatibility between TransformerBridge and HookedTransformer."""
 
     @pytest.mark.skip(
         reason="hook_mlp_out has known gradient differences due to architectural bridging (0.875 diff, but forward pass matches perfectly)"
     )
-    def test_backward_hook_gradients_match_hooked_transformer(self):
+    def test_backward_hook_gradients_match_hooked_transformer(
+        self, gpt2_hooked_unprocessed, gpt2_bridge_compat_no_processing
+    ):
         """Test that backward hook gradients match between TransformerBridge and HookedTransformer.
 
         This test ensures that backward hooks see identical gradient values in both
         TransformerBridge and HookedTransformer when using no_processing mode.
         """
-        hooked_model = HookedTransformer.from_pretrained_no_processing("gpt2", device_map="cpu")
-        bridge_model: TransformerBridge = TransformerBridge.boot_transformers(
-            "gpt2", device="cpu"
-        )  # type: ignore
-        bridge_model.enable_compatibility_mode(no_processing=True)
+        hooked_model = gpt2_hooked_unprocessed
+        bridge_model = gpt2_bridge_compat_no_processing
 
         test_input = torch.tensor([[1, 2, 3]])
 
@@ -51,16 +47,7 @@ def sum_bridge_grads(grad, hook=None):
             out = bridge_model(test_input)
             out.sum().backward()
 
-        print(f"HookedTransformer gradient sum: {hooked_grad_sum.item():.6f}")
-        print(f"TransformerBridge gradient sum: {bridge_grad_sum.item():.6f}")
-        print(f"Difference: {abs(hooked_grad_sum - bridge_grad_sum).item():.6f}")
         assert torch.allclose(hooked_grad_sum, bridge_grad_sum, atol=1e-2, rtol=1e-2), (
             f"Gradient sums should be identical but differ by "
             f"{abs(hooked_grad_sum - bridge_grad_sum).item():.6f}"
         )
-
-
-if __name__ == "__main__":
-    test = TestBackwardHookCompatibility()
-    test.test_backward_hook_gradients_match_hooked_transformer()
-    print("✅ Backward hook compatibility test passed!")

tests/acceptance/model_bridge/compatibility/test_hook_completeness.py

@@ -15,7 +15,7 @@
 from transformer_lens.benchmarks import benchmark_forward_hooks, benchmark_hook_registry
 from transformer_lens.model_bridge import TransformerBridge
 
-pytestmark = pytest.mark.skip(reason="Temporarily skipping hook completeness tests pending fixes")
+pytestmark = pytest.mark.slow
 
 # Diverse architectures for hook completeness testing
 MODELS_TO_TEST = [
@@ -71,7 +71,9 @@ def test_all_hooks_fire(self, model_name):
         test_text = "The quick brown fox"
 
         # Run benchmark - this will fail if hooks don't fire
-        result = benchmark_forward_hooks(bridge, test_text, reference_model=ht, tolerance=1e-3)
+        # tolerance=1e-2: some architectures (e.g., pythia) accumulate small floating-point
+        # differences across layers that exceed 1e-3 but are not meaningful divergences.
+        result = benchmark_forward_hooks(bridge, test_text, reference_model=ht, tolerance=1e-2)
 
         # Must pass - all hooks must fire
         assert result.passed, (

tests/acceptance/model_bridge/compatibility/test_hook_duplication.py

@@ -2,15 +2,13 @@
 
 import torch
 
-from transformer_lens import HookedTransformer
-from transformer_lens.model_bridge import TransformerBridge
 
-
-def test_TransformerBridge_compatibility_mode_calls_hooks_once():
+def test_TransformerBridge_compatibility_mode_calls_hooks_once(
+    gpt2_hooked_unprocessed, gpt2_bridge_compat_no_processing
+):
     """Regression test: hooks fire exactly once even with aliased HookPoint names."""
-    hooked_model = HookedTransformer.from_pretrained_no_processing("gpt2", device_map="cpu")
-    bridge_model: TransformerBridge = TransformerBridge.boot_transformers("gpt2", device="cpu")  # type: ignore
-    bridge_model.enable_compatibility_mode(no_processing=True)
+    hooked_model = gpt2_hooked_unprocessed
+    bridge_model = gpt2_bridge_compat_no_processing
 
     test_input = torch.tensor([[1, 2, 3]])
 
@@ -47,10 +45,9 @@ def count_bridge_calls(acts, hook):
     )
 
 
-def test_hook_mlp_out_aliasing():
+def test_hook_mlp_out_aliasing(gpt2_bridge_compat_no_processing):
     """Test that hook_mlp_out is properly aliased to mlp.hook_out in compatibility mode."""
-    bridge_model: TransformerBridge = TransformerBridge.boot_transformers("gpt2", device="cpu")  # type: ignore
-    bridge_model.enable_compatibility_mode(no_processing=True)
+    bridge_model = gpt2_bridge_compat_no_processing
 
     block0 = bridge_model.blocks[0]
 
@@ -61,10 +58,9 @@ def test_hook_mlp_out_aliasing():
     ), "hook_mlp_out should be aliased to mlp.hook_out (same object)"
 
 
-def test_stateful_hook_pattern():
+def test_stateful_hook_pattern(gpt2_bridge_compat_no_processing):
     """Test stateful closure pattern (circuit-tracer's cache-then-pop) with aliased hooks."""
-    bridge_model: TransformerBridge = TransformerBridge.boot_transformers("gpt2", device="cpu")  # type: ignore
-    bridge_model.enable_compatibility_mode(no_processing=True)
+    bridge_model = gpt2_bridge_compat_no_processing
 
     test_input = torch.tensor([[1, 2, 3]])
     block = bridge_model.blocks[0]

tests/acceptance/model_bridge/compatibility/test_legacy_hooked_transformer_coverage.py

@@ -29,8 +29,10 @@ def model_name(self, request):
         return request.param
 
     @pytest.fixture(scope="class")
-    def bridge_model(self, model_name):
-        """Create a TransformerBridge model for testing."""
+    def bridge_model(self, model_name, gpt2_bridge):
+        """Use session-scoped fixture for gpt2, load fresh for other models."""
+        if model_name == "gpt2":
+            return gpt2_bridge
         try:
             return TransformerBridge.boot_transformers(model_name, device="cpu")
         except Exception as e: