CODEWITHSUNDEEP
pythonunit-testingassertion
Tyler
Tyler

Reputation: 2639

How can I only show the custom error message for Python's unittest module

Using Python's unittest module, the assertion

self.assertTrue(a > b - 0.5 && a < b + 0.5, "The two values did not agree")

outputs the following on failure:

AssertionError: False is not true : The two values did not agree

I don't want the False is not true to be printed. Ideally, AssertionError shouldn't be printed either. Only The two values did not agree should be printed.

Can I do this?

Upvotes: 1

Views: 2504

Answers (1)

idjaw
idjaw

Reputation: 26600

You can supress the False is true part, however, one thing to keep in mind here, you are raising an exception, and what you are seeing is the standard output of an assertion being raised in Python. You want to see this. Furthermore, this is being called directly in the assertion methods, as you can see from the assertTrue below:

def assertTrue(self, expr, msg=None):
    """Check that the expression is true."""
    if not expr:
        msg = self._formatMessage(msg, "%s is not true" % safe_repr(expr))
        raise self.failureException(msg)

To supress the 'False is true' part, change the longMessage class attribute to False: 

class TestCompare(unittest.TestCase):

    longMessage = False

    def test_thing(self):
        self.assertTrue(5 == 6, "The two values did not agree")

Output: 

Failure
Traceback (most recent call last):
  File "/Users/XXX/dev/rough/test_this.py", line 21, in test_things
    self.assertTrue(5 == 6, "The two values did not agree")
AssertionError: The two values did not agree

Upvotes: 4

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