{"id":3690,"date":"2022-07-06T01:59:35","date_gmt":"2022-07-06T01:59:35","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=3690"},"modified":"2022-07-09T07:47:20","modified_gmt":"2022-07-09T07:47:20","slug":"python-unittest-coverage","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/python-unit-testing\/python-unittest-coverage\/","title":{"rendered":"Python unittest Coverage"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to use the Python unittest coverage command to generate a test coverage report.<\/p>\n\n\n\n

What is a test coverage #<\/a><\/h2>\n\n\n\n

Test coverage is a ratio between the number of lines executed by at least one test case and the total number of lines of the code base:<\/p>\n\n\n

test coverage = lines of code executed \/ total number of lines<\/code><\/span><\/pre>\n\n\n
The test coverage is also known as code coverage. <\/p>\n\n\n\n
The test coverage is often used to assess the quality of a test suite. If the test coverage is low e.g., 5%, it is an indicator that you’re not testing enough. <\/p>\n\n\n\n
However, the reverse may not be true. For example, 100% test coverage is not a guarantee that you have a good test suite. In other words, a test suite with high coverage can still be of poor quality.<\/p>\n\n\n\n
Unittest coverage example #<\/a><\/h2>\n\n\n\n
We’ll use the following project structure to demo the unittest<\/code> coverage. Note that you can get the source code from this tutorial<\/a>.<\/p>\n\n\n
D:\\python-unit-testing\n\u251c\u2500\u2500 shapes\n|  \u251c\u2500\u2500 circle.py\n|  \u251c\u2500\u2500 shape.py\n|  \u2514\u2500\u2500 square.py\n\u2514\u2500\u2500 test\n   \u251c\u2500\u2500 test_circle.py\n   \u251c\u2500\u2500 test_square.py\n   \u2514\u2500\u2500 __init__.py<\/code><\/span><\/pre>\n\n\n
To generate a coverage report, you need to carry out two steps:<\/p>\n\n\n\n
First, run the coverage module to generate the coverage data:<\/p>\n\n\n
python -m coverage run -m unittest<\/code><\/span><\/pre>\n\n\n
Second, turn the coverage data into a report:<\/p>\n\n\n
python -m coverage report<\/code><\/span><\/pre>\n\n\n
Output:<\/p>\n\n\n
Name                  Stmts   Miss  Cover\n-----------------------------------------\nshapes\\circle.py          9      0   100%\nshapes\\shape.py           4      0   100%\nshapes\\square.py          9      0   100%\ntest\\__init__.py          0      0   100%\ntest\\test_circle.py      14      0   100%\ntest\\test_square.py      14      0   100%\n-----------------------------------------\nTOTAL                    50      0   100%<\/code><\/span>Code language:<\/span> plaintext<\/span> (<\/span>plaintext<\/span>)<\/span><\/small><\/pre>\n\n\n
To generate the coverage report in HTML format, you change the option of the coverage module to HTML like this:<\/p>\n\n\n
python -m coverage html <\/code><\/span><\/pre>\n\n\n
Output:<\/p>\n\n\n
Wrote<\/span> HTML<\/span> report<\/span> to<\/span> htmlcov<\/span>\\index<\/span>.html<\/span><\/code><\/span>Code language:<\/span> CSS<\/span> (<\/span>css<\/span>)<\/span><\/small><\/pre>\n\n\n
The output indicates the location of the HTML coverage report htmlcov\\index.html<\/code> under the project folder. <\/p>\n\n\n\n
If you open the index.html file of the htmlcov<\/code> folder, it’ll look like the following:<\/p>\n\n\n\n
\"python<\/figure>\n\n\n\n
Examining unittest coverage detailed report #<\/a><\/h2>\n\n\n\n
First, add the perimeter()<\/code> method to the Circle<\/code> class as follows:<\/p>\n\n\n
import<\/span> math\nfrom<\/span> .shape import<\/span> Shape\n\n\nclass<\/span> Circle<\/span>(Shape)<\/span>:<\/span>\n    def<\/span> __init__<\/span>(self, radius: float)<\/span> -> None<\/span>:<\/span>\n        if<\/span> radius < 0<\/span>:\n            raise<\/span> ValueError('The radius cannot be negative'<\/span>)\n\n        self._radius = radius\n\n    def<\/span> area<\/span>(self)<\/span> -> float:<\/span>\n        return<\/span> math.pi * math.pow(self._radius, 2<\/span>)\n\n    def<\/span> perimeter<\/span>(self)<\/span> -> float:<\/span>\n        return<\/span> 2<\/span> * math.pi * self._radius\n<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Next, gather the coverage data by running the following command:<\/p>\n\n\n
python -m coverage run -m unittest<\/code><\/span><\/pre>\n\n\n
Then, generate the coverage report by executing the following command:<\/p>\n\n\n
python -m coverage report<\/code><\/span><\/pre>\n\n\n
Output:<\/p>\n\n\n
Name                  Stmts   Miss  Cover\n-----------------------------------------\nshapes\\circle.py         11      1    91%\nshapes\\shape.py           4      0   100%\nshapes\\square.py          9      0   100%\ntest\\__init__.py          0      0   100%\ntest\\test_circle.py      14      0   100%\ntest\\test_square.py      14      0   100%\n-----------------------------------------\nTOTAL                    52      1    98%<\/code><\/span>Code language:<\/span> plaintext<\/span> (<\/span>plaintext<\/span>)<\/span><\/small><\/pre>\n\n\n
The coverage now is 98% in total and 91% in the shape\\circle.py<\/code> module. This is because the perimeter()<\/code> method is not tested.<\/p>\n\n\n\n
After that, generate the coverage report in HTML format:<\/p>\n\n\n
python -m coverage html  <\/code><\/span><\/pre>\n\n\n
\"\"<\/figure>\n\n\n\n
The circle.py<\/code> has 11 statements. The test executes 10 of them and misses one statement. Therefore, the test coverage is 10\/11 ~ 91%.<\/p>\n\n\n\n
Finally, click the circle.py<\/code> module for the detailed report:<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
  • Use the python -m coverage run -m unittest<\/code> command to gather coverage data and the python -m coverage report<\/code> command to generate a coverage report.<\/li>
  • Use the python -m coverage html<\/code> to generate the test coverage report in HTML format.<\/li><\/ul>\n
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