CODEWITHSUNDEEP
c#asp.netunit-testing
Xaisoft
Xaisoft

Reputation: 46651

Why does this Microsoft Unit Test Fail?

I have a unit test and I the number that gets stored in the actual variable from the Distance calcuation is 6.07328028312884, yet it is still saying the test is failing. Why?

        double expected = 6.07328028312884; 
        double actual;
        actual = target.Distance((double)latitude, (double)longitude);
        actual = actual / 1000;

        Assert.AreEqual(expected, actual);

Upvotes: 1

Views: 136

Answers (3)

Felice Pollano
Felice Pollano

Reputation: 33272

As Matt said, is not a good idea to compare for equality two floats, use Math.Abs(expected-actual)<epsilon with a small epsilon.

Upvotes: 5

Armen Tsirunyan
Armen Tsirunyan

Reputation: 133092

I am not sure about Microsoft UT's, but in CPPUNIT there is a special macro

CPPUNIT_ASSERT_DOUBLES_EQUAL(expected, actual)

which probably checks that the absolute value of the difference of expected and actual is less than some epsilon. There has to be an analogous function in Microsoft UTs

Upvotes: 0

Matt Greer
Matt Greer

Reputation: 62057

floating point numbers are inaccurate by their very design. To test to that much accuracy is probably not going to work. What is the value of actual? you'll probably find it's off by expected just a tad, due to rounding and the general nature of floating point on computers.

Upvotes: 5

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