CODEWITHSUNDEEP
pythonunit-testingpython-unittest
Bula
Bula

Reputation: 1586

Programmaticaly detect if python code is being under test

How can python program know if it is being tested? For example:

def foo():
    if foo_being_tested:
        pseudorandom()
    else:
        random()

When in test, program should use pseudorandom sequence to be able to compare with C code version of the program and in regular execution random from numpy should be used.

Upvotes: 3

Views: 1492

Answers (1)

Martijn Pieters
Martijn Pieters

Reputation: 1121316

You can't, not without inspecting the call stack.

Generally speaking, you should not do this at all; by altering your code when tested you are not correctly testing your code.

Instead, you'd use mocking to replace any parts your code uses (anything used by the code under test but not part of it). For your specific example, you'd mock out random(); on Python 3.3 and up you can use unittest.mock, available as mock on PyPI for other Python versions, or you can just manually swap out module_under_test.random for the duration of the test.

You could also set an environment variable in your unittests to make it explicit you are running a test, but ideally that should be avoided.

Upvotes: 6

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