coverage_two_functions.py

import io
import coverage
import json
from contextlib import redirect_stdout


def functions_execution_is_identical(func1, func2, file_to_compare):
    """
    Compare the coverage of two functions to see if they're equivalent/same.

    Say you have `test_thing()` and someone else wrote a `test_thing_better()` and you want to see if they 
    are indeed the same.

    In the same file that test_thing and test_thing_better are, add a new function `test_are_things_the_same`:

    def test_thing(...)
        ...
        utils.thing(...)
        ...

    def test_thing_better(...)
        ...
        utils.thing(...)
        ...

    def test_are_things_the_same():
        from functools import partial
        functions_execution_is_identical(partial(test_thing, arg1, kwarg1=123), 
                                         partial(test_thing_better, arg1, kwarg1=123)
                                         'path/to/utils.py')

    # if `test_are_things_the_same` does not crash, that means the two tests are equivalent.
    """

    # Run coverage for the first function
    func1_cov = coverage.Coverage()
    func1_cov.start()

    func1()

    func1_cov.stop()

    # Run coverage for the second function
    func2_cov = coverage.Coverage()
    func2_cov.start()

    func2()

    func2_cov.stop()

    # Generate the json reports
    with io.StringIO() as buf, redirect_stdout(buf):
        func1_cov.json_report(pretty_print=True, outfile='-')
        func1_json = json.loads(buf.getvalue())

    with io.StringIO() as buf, redirect_stdout(buf):
        func2_cov.json_report(pretty_print=True, outfile='-')
        func2_json = json.loads(buf.getvalue())

    # Compare that the functions 1 and 2 executed the exact lines of code in the fine in question
    assert func1_json['files'][file_to_compare] == func2_json['files'][file_to_compare]