为什么我在 Python 中遇到断言错误？

Question

I am testing a function in Python. This is the function I wrote.

def hypotenuse(a, b):
   math.sqrt(a**2 + b**2)

I used this test case.

def test_hypotenuse_1(self):
   self.assertEqual(funcs.hypotenuse, 3, 4)

This assertion error came up.

======================================================================
FAIL: test_hypotenuse_1 (__main__.TestCases)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "funcs_tests.py", line 27, in test_hypotenuse_1
    self.assertEqual(funcs.hypotenuse, 3, 4)
AssertionError: <function hypotenuse at 0x7f397f2d79d8> != 3 : 4

What did I do wrong? Sorry if this is a basic question I am a first-time coder.

Answer 1

You need to call the function, and then specify what the result of that call is supposed to be equal to

def test_hypotenuse_1(self):
    self.assertEqual(funcs.hypotenuse(3, 4), 5)

This asserts that the hypotenuse of a triangle with sides 3 and 4 is equal to 5.

Your test will still fail because hypotenuse() doesn't return the result. It needs to be:

def hypotenuse(a, b):
    return math.sqrt(a**2 + b**2)

Note that you should generally not use equality testing for a mathematical function like this. It uses floating point arithmetic, which can have roundoff error. You can use the assertAlmostEqual() function for this.