Python unittest – assertIs() function

assertIs() in Python is a unittest library function that is used in unit testing to test whether first and second input value evaluates to the same object or not. This function will take three parameters as input and return a boolean value depending upon the assert condition. If both input evaluates to the same object then assertIs() will return true else return false.

Syntax: assertIs(firstValue, secondValue, message)

Parameters: assertIs() accept three parameters which are listed below with explanation:

• firstValue  variable of any type which is used in the comparison by function
• secondValue: variable of any 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

Output:

F
======================================================================
FAIL: test_negative (__main__.TestMethods)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "p1.py", line 15, in test_negative
    self.assertIs(firstValue, secondValue, message)
AssertionError: <__main__.DummyClass object at 0x7f1d20251b70> is 
not <__main__.DummyClass object at 0x7f1d20251ba8> :
 First value and second value are not evaluated to same object!

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

FAILED (failures=1)

Example 2: Positive Test case

Output:

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

OK

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