Menu
Python's built-in unittest module makes assertions with TestCase.assert* methods:
class FooTest(TestCase): def test_foo(self): self.assertEqual(1,1) self.assertNotEqual(1,2) self.assertTrue(True) I have generally used a testrunner such as nose or py.test which allow use of the built-in assert keyword when making assertions:
assert 1 == 1 assert 1 != 2 assert True What is the motivation for unittest's TestCase.assert* approach and what are the strengths and weaknesses of this vs asserting with the built-in assert keyword? Are there reasons why unittest's syntax should be favoured?
648
The assert section ensures that the code behaves as expected. Assertions replace us humans in checking that the software does what it should. They express requirements that the unit under test is expected to meet. Now, often one can write slightly different assertions to capture a given requirement.
Python testing framework uses Python's built-in assert() function which tests a particular condition. If the assertion fails, an AssertionError will be raised. The testing framework will then identify the test as Failure. Other exceptions are treated as Error.
assertFalse() in Python is a unittest library function that is used in unit testing to compare test value with false. This function will take two parameters as input and return a boolean value depending upon the assert condition. If test value is false then assertFalse() will return true else return false.
Assert statements are used to debug code and handle errors. You should not use an assert statement in a production environment. Debugging is a crucial part of programming in any language. When debugging programs in Python, there may be times when you want to test for a certain condition.
The problem with the assert keyword is that it is optimized out, and thus ignored, when Python is run in 'optimized' mode (with the -O argument or with the PYTHONOPTIMIZE environment variable set.) If tests were to use assert then testing with -O would be impossible.
Additionally, the use of the assert methods makes it trivial to report about what the values involved actually were, without having to dig into the stack and the source and figure out what they were supposed to be (which, I believe, is the technique nose and py.test use for this.)
76
I don't see a concrete design decision for this. Looking at the unittest docs it states that
the type specific equality function will be called in order to generate a more useful default error message
So I would say it is an implementation decision to help produce more meaningful errors etc.
32
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
