How to display the right coverage for unit-tests in python?

Question

I am having trouble displaying the correct coverage info for unittest. I created a simple python file as such: simple.py that contains the following contents:

def multiply(x, y):
    return x * y

def add(x, y):
    return x + y

def subtract(x, y):
    return x - y

def divide(x, y):
    return x / y

and a unittest as such called test_simple.py that i stored under the tests folder:

import unittest

import simple as si


class TestSimple(unittest.TestCase):
    def test_multiply(self):
        self.assertEqual(si.multiply(3, 4), 12)

Now, im. using pytest and coverage.py to run my coverage report. I ran the following statements:

pytest test_simple.py --cov=simple

and see the following:

coverage report -m

Name        Stmts   Miss  Cover   Missing
---------------------------------------------------------------------------------------------------------------
simple.py       8      3    62%   5, 8, 11
---------------------------------------------------------------------------------------------------------------
TOTAL           8      3    62%

Why would this show 62%? shouldn't it 25%? it seems its adding 100% from my test file and 25% from the file i want to see how much percent is covered, and taking the average of the two...which gives me 62.5%. is there anyway i can show the correct info which is 25%? thanks

larsks · Accepted Answer · 2024-02-09 04:41:39Z

2

Take a look at the HTML output (pytest --cov=simple --cov-report=html, then open htmlcov/index.html), and you may find the answer more obvious:

The metrics are reporting coverage based on the number of statements in your code. Not "number of functions". There are 8 statements in your code:

4 def statements
4 return statements

Your tests execute all four def statements, because that's what happens when you import a file, and then one return statement (for the multiply function).

>>> 5/8
0.625

answered Feb 9, 2024 at 4:41

larsks

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4 Comments

turtle_in_mind Over a year ago

Hey even when I do from simple import multiply, it’s showing 4 def statements as being covered and 3 return statements as not being covered. Is there anyway I can show just the functions not being covered?

larsks Over a year ago

No. Importing a file executes all the top-level statements (function and class definitions and any other "bare code").

turtle_in_mind Over a year ago

when I do from simple import multiply, you are telling me it’s importing the whole file even though I’m importing only one function?

larsks Over a year ago

That's correct. Python doesn't know what functions are declared in that file until after it has executed all the top-level statements.

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