The side cannot be negative and the tests always expect a positive value (that's what the log tells you, though not clearly: your answer is -7 and it should be 7), there is a problem with your code, not with the tests.

For Python - breaked tests

Should be -7: -7 should equal 7
Should be -9: -9 should equal 9

Even my fucntion return for example 25 - the error message doesn't change

Please use code blocks when pasting code.