[issue38296] unittest expectedFailure does not differentiate errors from failures

[Terry J. Reedy]

Terry J. Reedy <tjreedy at udel.edu> added the comment:

A test either passes or fails.  Like a not operator, the expectedFailure decorator inverts the result.

https://docs.python.org/3/library/unittest.html#unittest.expectedFailure
@unittest.expectedFailure
    Mark the test as an expected failure. If the test fails it will be considered a success. If the test passes, it will be considered a failure.

By itself, your 'test' method fails.  Decorated, it should and does pass.

As you suggested, using expectedFailure is a blunt instrument that can be misleading if not used carefully and not reviewed when editing the module tested.  It is only used 7 times in test_xyz.py modules in the lib/test directory and subdirectories.

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nosy: +ezio.melotti, michael.foord
versions:  -Python 3.5, Python 3.6

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<https://bugs.python.org/issue38296>
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