Python unittest – assertTrue() function

assertTrue() in Python is a unittest library function that is used in unit testing to compare test value with true. This function will take two parameters as input and return a boolean value depending upon the assert condition. If test value is true then assertTrue() will return true else return false.

Syntax: assertTrue(testValue, message)

Parameters: assertTrue() accepts two parameters which are listed below with explanation:

• testValue:  variable of boolean type which is used in the comparison by function
• message: a string sentence as a message which got displayed when the test case got failed.

Listed below are two different examples illustrating the positive and negative test case for given assert function:

Example 1: Negative Test case

Python3

# unit test case
import unittest

class TestStringMethods(unittest.TestCase):
    # test function
    def test_negative(self):
        testValue = False
        # error message in case if test case got failed
        message = "Test value is not true."
        # assertTrue() to check true of test value
        self.assertTrue( testValue, message)

if __name__ == '__main__':
    unittest.main()

Output:

F
======================================================================
FAIL: test_negative (__main__.TestStringMethods)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "p1.py", line 11, in test_negative
    self.assertTrue( testValue, message)
AssertionError: False is not true : Test value is not true.

----------------------------------------------------------------------
Ran 1 test in 0.000s

FAILED (failures=1)

Example 2: Positive Test case

Python3

# unit test case
import unittest

class TestStringMethods(unittest.TestCase):
    # test function
    def test_positive(self):
        testValue = True
        # error message in case if test case got failed
        message = "Test value is not true."
        # assertTrue() to check true of test value
        self.assertTrue( testValue, message)

if __name__ == '__main__':
    unittest.main()

Output:

.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK

Reference: https://docs.python.org/3/library/unittest.html