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Lib/unittest/__init__.py

cpython 3.14 @ ab2d84fe1023/Lib/unittest/__init__.py

Lib/unittest/__init__.py re-exports the key symbols from the unittest sub-package. The implementation is spread across several submodules; this annotation covers the overall architecture.

Map​

LinesSymbolRole
1-50Re-exportsTestCase, TestSuite, TestLoader, TestResult, TestRunner
unittest/case.pyTestCaseAssert methods, setUp/tearDown lifecycle, subTest
unittest/suite.pyTestSuiteOrdered collection of tests, recursive run
unittest/loader.pyTestLoaderClass/module/file discovery via loadTestsFrom*
unittest/runner.pyTextTestRunnerRuns a suite and prints results to a stream
unittest/result.pyTestResultAccumulates pass/fail/error/skip counts

Reading​

TestCase.assertEqual and the comparison dispatch​

assertEqual first tries type(first) against _type_equality_funcs (a dict mapping types to specialized comparers such as assertListEqual, assertDictEqual) before falling back to ==. This produces richer diffs for collections.

# CPython: Lib/unittest/case.py:870 assertEqual
def assertEqual(self, first, second, msg=None):
    if not first == second:
        firstclass = first.__class__
        secondclass = second.__class__
        if firstclass is secondclass:
            assertion_func = self._type_equality_funcs.get(firstclass)
            if assertion_func is not None:
                assertion_func(first, second, msg=msg)
                return
        ...
        raise self.failureException(...)

subTest context manager​

subTest(msg, **params) temporarily overrides the test's description so that failures inside the block report the subtest parameters. A failure inside subTest does not abort the test method; subsequent subTest blocks continue executing.

TestLoader.discover​

discover(start_dir, pattern='test*.py') walks the directory tree with os.walk, imports matching files, and calls loadTestsFromModule on each. Files whose import raises an exception produce an error test rather than crashing the discovery.

@skip and @expectedFailure​

@skip(reason) wraps the test method to raise SkipTest immediately. @expectedFailure wraps the method and inverts the result: a failure is counted as a pass, and a pass is counted as an unexpected success (which is reported as a failure).

gopy notes​

Not yet ported. The unittest dependency is needed for the v0.12.1 e2e test gate (feat/v0.12.1-test-e2e). Planned path: module/unittest/. The assert methods are independent of the VM; TestLoader.discover requires os.walk and importlib.