[Backend Test] Backend test reporting skeleton (#12296)

### Summary
Add the initial skeleton of reporting code for the backend tester. This
PR is primarily focused on putting the hooks and runner structure in
place. Follow-up work will expand the scope of collection and reporting
outputs.

This PR adds the following:
- CLI runner for the test suite.
- Basic test result breakdown by success / fail and cause (failing in
lowering vs output mismatch, for example).
- Refactoring of test suite logic to clean things up.

Next steps:
- Aggregate results by flow (backend).
- Add additional CLI flags to allow filtering backends and dtypes.
- Land more of the operator test suite.
- Wire up flows for quantized operators.

Note that this PR is stacked on (and thus includes)
#11960. I accidently broke my
ghstack, so I'm converting this to a normal PR.

Sample output (XNNPACK):
```
Test Session Summary:

   84 Passed / 95
   11 Failed / 95
    0 Skipped / 95

[Success]
   66 Delegated
   18 Undelegated

[Failure]
    4 Lowering Fail
    0 PTE Load Fail
    0 PTE Run Fail
    6 Output Mismatch Fail
```
Reproduce with `ET_TEST_ENABLED_BACKENDS=xnnpack python -m
executorch.backends.test.suite.runner.executorch.backends.test.suite`.
I've temporarily commented out non-f32 dtypes to work around some
crashes in XNNPACK, which are non-recoverable from Python.

Author: GregoryComer

backends/test/suite/README.md

@@ -4,6 +4,39 @@ This directory contains tests that validate correctness and coverage of backends
 
 These tests are intended to ensure that backends are robust and provide a smooth, "out-of-box" experience for users across the full span of input patterns. They are not intended to be a replacement for backend-specific tests, as they do not attempt to validate performance or that backends delegate operators that they expect to.
 
+## Running Tests and Interpreting Output
+Tests can be run from the command line, either using the runner.py entry point or the standard Python unittest runner. When running through runner.py, the test runner will report test statistics, including the number of tests with each result type.
+
+Backends can be specified with the `ET_TEST_ENABLED_BACKENDS` environment variable. By default, all available backends are enabled. Note that backends such as Core ML or Vulkan may require specific hardware or software to be available. See the documentation for each backend for information on requirements.
+
+Example:
+```
+ET_TEST_ENABLED_BACKENDS=xnnpack python -m executorch.backends.test.suite.runner
+```
+
+```
+2465 Passed / 2494
+16 Failed
+13 Skipped
+
+[Success]
+736 Delegated
+1729 Undelegated
+
+[Failure]
+5 Lowering Fail
+3 PTE Run Fail
+8 Output Mismatch Fail
+```
+
+Outcomes can be interpreted as follows:
+ * Success (delegated): The test passed and at least one op was delegated by the backend.
+ * Success (undelegated): The test passed with no ops delegated by the backend. This is a pass, as the partitioner works as intended.
+ * Skipped: test fails in eager or export (indicative of a test or dynamo issue).
+ * Lowering fail: The test fails in to_edge_transform_and_lower.
+ * PTE run failure: The test errors out when loading or running the method.
+ * Output mismatch failure: Output delta (vs eager) exceeds the configured tolerance.
+
 ## Backend Registration
 
 To plug into the test framework, each backend should provide an implementation of the Tester class, defined in backends/test/harness/tester.py. Backends can provide implementations of each stage, or use the default implementation, as appropriate.

backends/test/suite/__init__.py

@@ -16,6 +16,9 @@
 
 import torch
 from executorch.backends.test.harness import Tester
+from executorch.backends.test.suite.context import get_active_test_context, TestContext
+from executorch.backends.test.suite.reporting import log_test_summary
+from executorch.backends.test.suite.runner import run_test, runner_main
 
 logger = logging.getLogger(__name__)
 logger.setLevel(logging.INFO)
@@ -60,17 +63,17 @@ def is_backend_enabled(backend):
 
 
 DTYPES = [
-    torch.int8,
-    torch.uint8,
-    torch.int16,
-    torch.uint16,
-    torch.int32,
-    torch.uint32,
-    torch.int64,
-    torch.uint64,
-    torch.float16,
+    # torch.int8,
+    # torch.uint8,
+    # torch.int16,
+    # torch.uint16,
+    # torch.int32,
+    # torch.uint32,
+    # torch.int64,
+    # torch.uint64,
+    # torch.float16,
     torch.float32,
-    torch.float64,
+    # torch.float64,
 ]
 
 FLOAT_DTYPES = [
@@ -117,16 +120,19 @@ def _expand_test(cls, test_name: str):
     delattr(cls, test_name)
 
 
-def _make_wrapped_test(test_func, *args, **kwargs):
+def _make_wrapped_test(
+    test_func: Callable,
+    test_name: str,
+    test_flow: str,
+    tester_factory: Callable,
+    params: dict | None = None,
+):
     def wrapped_test(self):
-        test_func(self, *args, **kwargs)
+        with TestContext(test_name, test_flow, params):
+            test_kwargs = params or {}
+            test_kwargs["tester_factory"] = tester_factory
 
-    return wrapped_test
-
-
-def _make_wrapped_dtype_test(test_func, dtype, tester_factory):
-    def wrapped_test(self):
-        test_func(self, dtype, tester_factory)
+            test_func(self, **test_kwargs)
 
     return wrapped_test
 
@@ -140,37 +146,63 @@ def _create_test_for_backend(
     test_type = getattr(test_func, "test_type", TestType.STANDARD)
 
     if test_type == TestType.STANDARD:
-        wrapped_test = _make_wrapped_test(test_func, tester_factory)
+        wrapped_test = _make_wrapped_test(
+            test_func, test_func.__name__, flow_name, tester_factory
+        )
         test_name = f"{test_func.__name__}_{flow_name}"
         setattr(cls, test_name, wrapped_test)
     elif test_type == TestType.DTYPE:
         for dtype in DTYPES:
-            # wrapped_test = _make_wrapped_dtype_test(test_func, dtype, tester_factory)
-            wrapped_test = _make_wrapped_test(test_func, dtype, tester_factory)
+            wrapped_test = _make_wrapped_test(
+                test_func,
+                test_func.__name__,
+                flow_name,
+                tester_factory,
+                {"dtype": dtype},
+            )
             dtype_name = str(dtype)[6:]  # strip "torch."
             test_name = f"{test_func.__name__}_{dtype_name}_{flow_name}"
             setattr(cls, test_name, wrapped_test)
     else:
         raise NotImplementedError(f"Unknown test type {test_type}.")
 
 
+def load_tests(loader, suite, pattern):
+    package_dir = os.path.dirname(__file__)
+    discovered_suite = loader.discover(
+        start_dir=package_dir, pattern=pattern or "test_*.py"
+    )
+    suite.addTests(discovered_suite)
+    return suite
+
+
 class OperatorTest(unittest.TestCase):
     def _test_op(self, model, inputs, tester_factory):
-        tester = (
-            tester_factory(
-                model,
-                inputs,
-            )
-            .export()
-            .to_edge_transform_and_lower()
+        context = get_active_test_context()
+
+        # This should be set in the wrapped test. See _make_wrapped_test above.
+        assert context is not None, "Missing test context."
+
+        run_summary = run_test(
+            model,
+            inputs,
+            tester_factory,
+            context.test_name,
+            context.flow_name,
+            context.params,
         )
 
-        is_delegated = any(
-            n.target == torch._higher_order_ops.executorch_call_delegate
-            for n in tester.stages[tester.cur].graph_module.graph.nodes
-            if n.op == "call_function"
-        )
+        log_test_summary(run_summary)
+
+        if not run_summary.result.is_success():
+            if run_summary.result.is_backend_failure():
+                raise RuntimeError("Test failure.") from run_summary.error
+            else:
+                # Non-backend failure indicates a bad test. Mark as skipped.
+                raise unittest.SkipTest(
+                    f"Test failed for reasons other than backend failure. Error: {run_summary.error}"
+                )
+
 
-        # Only run the runtime test if the op was delegated.
-        if is_delegated:
-            (tester.to_executorch().serialize().run_method_and_compare_outputs())
+if __name__ == "__main__":
+    runner_main()

backends/test/suite/context.py

@@ -0,0 +1,28 @@
+# Test run context management. This is used to determine the test context for reporting
+# purposes.
+class TestContext:
+    def __init__(self, test_name: str, flow_name: str, params: dict | None):
+        self.test_name = test_name
+        self.flow_name = flow_name
+        self.params = params
+
+    def __enter__(self):
+        global _active_test_context
+        import sys
+
+        if _active_test_context is not None:
+            print(f"Active context: {_active_test_context.test_name}", file=sys.stderr)
+        assert _active_test_context is None
+        _active_test_context = self
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        global _active_test_context
+        _active_test_context = None
+
+
+_active_test_context: TestContext | None = None
+
+
+def get_active_test_context() -> TestContext | None:
+    global _active_test_context
+    return _active_test_context

backends/test/suite/reporting.py

@@ -0,0 +1,163 @@
+from collections import Counter
+from dataclasses import dataclass
+from enum import IntEnum, nonmember
+
+
+class TestResult(IntEnum):
+    """Represents the result of a test case run, indicating success or a specific failure reason."""
+
+    SUCCESS = 0
+    """ The test succeeded with the backend delegate part or all of the graph. """
+
+    SUCCESS_UNDELEGATED = 1
+    """ The test succeeded without the backend delegating anything. """
+
+    EAGER_FAIL = 2
+    """ The test failed due to the model failing to run in eager mode. """
+
+    EXPORT_FAIL = 3
+    """ The test failed due to the model failing to export. """
+
+    LOWER_FAIL = 4
+    """ The test failed due to a failure in partitioning or lowering. """
+
+    PTE_LOAD_FAIL = 5
+    """ The test failed due to the resulting PTE failing to load. """
+
+    PTE_RUN_FAIL = 6
+    """ The test failed due to the resulting PTE failing to run. """
+
+    OUTPUT_MISMATCH_FAIL = 7
+    """ The test failed due to a mismatch between runtime and reference outputs. """
+
+    UNKNOWN_FAIL = 8
+    """ The test failed in an unknown or unexpected manner. """
+
+    @nonmember
+    def is_success(self):
+        return self in {TestResult.SUCCESS, TestResult.SUCCESS_UNDELEGATED}
+
+    @nonmember
+    def is_non_backend_failure(self):
+        return self in {TestResult.EAGER_FAIL, TestResult.EAGER_FAIL}
+
+    @nonmember
+    def is_backend_failure(self):
+        return not self.is_success() and not self.is_non_backend_failure()
+
+    @nonmember
+    def display_name(self):
+        if self == TestResult.SUCCESS:
+            return "Success (Delegated)"
+        elif self == TestResult.SUCCESS_UNDELEGATED:
+            return "Success (Undelegated)"
+        elif self == TestResult.EAGER_FAIL:
+            return "Fail (Eager)"
+        elif self == TestResult.EXPORT_FAIL:
+            return "Fail (Export)"
+        elif self == TestResult.LOWER_FAIL:
+            return "Fail (Lowering)"
+        elif self == TestResult.PTE_LOAD_FAIL:
+            return "Fail (PTE Load)"
+        elif self == TestResult.PTE_RUN_FAIL:
+            return "Fail (PTE Run)"
+        elif self == TestResult.OUTPUT_MISMATCH_FAIL:
+            return "Fail (Output Mismatch)"
+        elif self == TestResult.UNKNOWN_FAIL:
+            return "Fail (Other)"
+        else:
+            raise ValueError(f"Invalid TestResult value: {self}.")
+
+
+@dataclass
+class TestCaseSummary:
+    """
+    Contains summary results for the execution of a single test case.
+    """
+
+    name: str
+    """ The qualified name of the test, not including the flow suffix. """
+
+    flow: str
+    """ The backend-specific flow name. Corresponds to flows registered in backends/test/suite/__init__.py. """
+
+    params: dict | None
+    """ Test-specific parameters, such as dtype. """
+
+    result: TestResult
+    """ The top-level result, such as SUCCESS or LOWER_FAIL. """
+
+    error: Exception | None
+    """ The Python exception object, if any. """
+
+
+class TestSessionState:
+    test_case_summaries: list[TestCaseSummary]
+
+    def __init__(self):
+        self.test_case_summaries = []
+
+
+@dataclass
+class RunSummary:
+    aggregated_results: dict[TestResult, int]
+    num_test_cases: int
+    test_case_summaries: list[TestCaseSummary]
+    total_failed: int
+    total_passed: int
+    total_skipped: int
+
+    @classmethod
+    def from_session(cls, session: TestSessionState) -> "RunSummary":
+        # Total each outcome type.
+        aggregated_results = dict(
+            sorted(Counter(s.result for s in session.test_case_summaries).items())
+        )
+
+        total_failed = 0
+        total_passed = 0
+        total_skipped = 0
+
+        for k, v in aggregated_results.items():
+            if k.is_success():
+                total_passed += v
+            elif k.is_backend_failure():
+                total_failed += v
+            else:
+                total_skipped += v
+
+        return cls(
+            aggregated_results=aggregated_results,
+            num_test_cases=len(session.test_case_summaries),
+            test_case_summaries=session.test_case_summaries,
+            total_failed=total_failed,
+            total_passed=total_passed,
+            total_skipped=total_skipped,
+        )
+
+
+_active_session: TestSessionState | None = None
+
+
+def begin_test_session():
+    global _active_session
+
+    assert _active_session is None, "A test session is already active."
+    _active_session = TestSessionState()
+
+
+def log_test_summary(summary: TestCaseSummary):
+    global _active_session
+
+    if _active_session is not None:
+        _active_session.test_case_summaries.append(summary)
+
+
+def complete_test_session() -> RunSummary:
+    global _active_session
+
+    assert _active_session is not None, "No test session is active."
+    summary = RunSummary.from_session(_active_session)
+    _active_session = None
+
+    return summary