assertIn() in Python is a unittest library function that is used in unit testing to check whether a string is contained in other or not. This function will take three string parameters as input and return a boolean value depending upon the assert condition. If the key is contained in container string it will return true else it returns false.
Syntax: assertIn(key, container, message)
Parameters: assertIn() accept three parameters which are listed below with explanation:
- key: a string whose presence is checked in the given container
- container: a string in which key string is searched
- 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
# test suite import unittest
class TestStringMethods(unittest.TestCase):
# test function to test whether key is present in container
def test_negative( self ):
key = "gfg"
container = "geeksforgeeks"
# error message in case if test case got failed
message = "key is not in container."
# assertIn() to check if key is in container
self .assertIn(key, container, message)
if __name__ = = '__main__' :
unittest.main()
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Output:
F ====================================================================== FAIL: test_negative (__main__.TestStringMethods) ---------------------------------------------------------------------- Traceback (most recent call last): File "/home/e920f2cd9195a3fd72bd531f7f101754.py", line 12, in test_negative self.assertIn(key, container, message) AssertionError: 'gfg' not found in 'geeksforgeeks' : key is not in container. ---------------------------------------------------------------------- Ran 1 test in 0.001s FAILED (failures=1)
Example 2: Positive Test case
# test suite import unittest
class TestStringMethods(unittest.TestCase):
# test function to test whether key is present in container
def test_positive( self ):
key = "geeks"
container = "geeksforgeeks"
# error message in case if test case got failed
message = "key is not in container."
# assertIn() to check if key is in container
self .assertIn(key, container, message)
if __name__ = = '__main__' :
unittest.main()
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Output:
. ---------------------------------------------------------------------- Ran 1 test in 0.000s OK
Reference: https://docs.python.org/3/library/unittest.html