[Python] What I did to do Unit Test

table of contents


Someone who can do a little operation on a black screen The specs can be anything as long as Python works

What is Unit Test in the first place?

Unit test(Unit test)What is|Software validation type|Techmatrix Corporation

It refers to testing whether a program is functioning properly with the smallest particle size that makes up the program, such as the methods of the program. In the IT industry, it is also called unit testing.

There are libraries that do unit tests in each language. Below is an example

As an aside, in Ruby etc., Minitest and Rspec etc. have a unit test mechanism.

What do you need to do to test?

To execute Unit Test in Python, write a Py file to write the test code.

Please refer to the official Japanese documentation for writing detailed tests.

unittest — unit test framework — Python 3.8.6 documentation

Create the following files using VSCode etc.

In this case, we have listed a test case that intentionally fails.


import unittest

class TestStringMethods(unittest.TestCase):

    def test_false(self): 
        self.assertFalse("hoge", "hoge")

if __name__ == '__main__':

Next, try running the program on the console.

When executing on the CLI, you can execute UnitTest with the following command.

python3 -m unittest sample.py

FAIL: test_false (test.sample.TestStringMethods)
Traceback (most recent call last):
  File "/Users/pcuser/Documents/GitHub/pysecret/test/sample.py", line 6, in test_false
    self.assertFalse("hoge", "hoge")
AssertionError: 'hoge' is not false : hoge

Ran 1 test in 0.001s

FAILED (failures=1)

If FAILD is displayed and it fails like this, it's OK If ERROR is displayed, it may be a grammatical problem in Python, so please google it.

Some common errors in Python are: [Enter a reference error message]

Can't call the method?

After this, we will actually describe the test cases.

In order to make the test as practical as possible, create a program to be tested.


def helloMethod(str):
    msg = str
    return msg

if __name__ == '__main__':

Then add ʻinport hello` to test.py so that helloMethod can be called.

import unittest
import hello <-Like this

Information to be input What is the information to be output?

This time I created a method to do a simple Echolalia. What you pass as input is the str variable of the string you pass in the method argument. And the expected value is that str will be returned as output when the method is executed.

import unittest
import hello

class TestStringMethods(unittest.TestCase):

    # def test_false(self):
    #     self.assertFalse("hoge", "hoge")
    def test_hello(self):
        input_str =  "Hello"
        msg = hello.helloMethod(input_str)
        self.assertEqual(msg, input_str)

if __name__ == '__main__':

What do I need to do to pass the test?

To verify that the result is correct, use the Assert method with the value stored in the msg variable. Make sure that the values of input_str are the same.

As a way of writing, since the Assert method of the UnitTest class is used, use self.assertEqual.

Since it has already been written on the source, execute the same command that confirmed the start of UnitTest itself again.

python3 -m unittest sample.py

Ran 1 test in 0.000s


If you see the word OK on the console, the test is successful.

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