I have written a test case which shows the error

```
from unittest import *
class MyTest(unittest.TestCase):
    def test_add(self):
        self.assertEquals(1,(2-1),"Sample Subraction Test")

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

```

Output:
Str object is not callable

Instead of 
"from unittest import \*" I have given 
"import unittest"

it worked

but still i couldn't get point it accurately 
what might be the reason for this?