How to test multiple return values with python?

Question

So I have this function which returns sine and cosine and another basic unittest function which is supposed to test both return values with assertEqual, but I don't know how to test both of the return values. What's the best way to do that?

def calc_sin_cos(sindeg, cosdeg):
    sine = math.sin(math.radians(sindeg))
    cosine = math.cos(math.radians(cosdeg))

    return sine, cosine

def test_calc_sin_cos(self):
    sine = 2
    cosine = 2
    result = myscript.calc_sin_cos(sine, cosine)
    self.assertEqual(result, 0.03489949670250097, 0.9993908270190958)

Obviously the above assertEqual doesn't work properly as it is.

It is important to understand, you can ever only have a single return value. You are returning a tuple of length 2 — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Mar 10, 2021 at 17:40

azro · Accepted Answer · 2021-03-10 17:40:17Z

2

When the method returns multiple values, it is a tuple in fact, the 2 following lines are identical:

return sine, cosine
return (sine, cosine)

For the calling method, these are same

result = myscript.calc_sin_cos(sine, cosine)
sin, cos = myscript.calc_sin_cos(sine, cosine)

To test them use assertEqual

with both values so as a tuple

result = myscript.calc_sin_cos(sine, cosine)
self.assertEqual(result, (0.03489949670250097, 0.9993908270190958))

or both values individually

sin, cos = myscript.calc_sin_cos(sine, cosine)
self.assertEqual(sin, 0.03489949670250097)
self.assertEqual(cos, 0.9993908270190958)

For float values, it can use useful to use unittest.assertAlmostEqual

  self.assertAlmostEqual(sin, 0.034, places=3)
  self.assertAlmostEqual(cos, 0.999, places=3)

answered Mar 10, 2021 at 17:40

azro

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