CODEWITHSUNDEEP
rubyunit-testingminitest
sudoremo
sudoremo

Reputation: 2402

Get 'backtrace' of an assertion error in ruby unit testing

When creating a helper method for unit testing, the console output of the failure only indicates the line where the actual assertion happened.

# Just an example method.
def test_equal(a, b)
  assert_equal a, b # Error indicates this line
end

test_equal(1, 2) # I'd like to know this line
test_equal(2, 3)

Is there a way of showing something like a "backtrace" or provide more context for these assertion errors?

Upvotes: 4

Views: 385

Answers (1)

sudoremo
sudoremo

Reputation: 2402

I've analyzed this matter further and stumbled across minitest's method Assertion.location. There, it goes through the backtrace (failed assertions result in exceptions of type Minitest::Assertion < Exception), reverses it and looks for methods starting with one of the following keywords:

  • assert
  • refute
  • flunk
  • pass
  • fail
  • raise
  • must
  • wont

Therefore, the example in the original question should look like the following:

# Just an example method.
def assert_my_equal(a, b)
  assert_equal a, b # Error indicates this line
end

assert_my_equal(1, 2) # This is the line number indicated in the failure report
assert_my_equal(2, 3)

This also explains why the Rails-specific assertion methods behave correctly: They start with assert_.

Upvotes: 7

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