Question

I’m using MSTest for testing and when I want to apply more inputs then the test looks like this:

[TestMethod]
public void SumTest()
{
  // data to test
  var items = new [] {
    new { First = 1, Second = 1, Expected = 2 },
    new { First = -1, Second = 1, Expected = 0 },
    new { First = 1, Second = 2, Expected = 3 },
    new { First = 1, Second = -1, Expected = 0 },
  };

  ICalculator target = GetSum(); // can be in the loop body

  foreach(var item in items)
  {
    var actual = target.Sum(item.First, item.Second);
    Assert.AreEqual(item.Expected, actual);
  }
}

I feel that this kind of testing is not the right way. I.e. I would like to separate testing data generation and testing itself.

I know, there is “data driven test” support in MSTest but it isn’t sufficient for me:

1. The items collection cannot be generated using some algorithm.
2. I cannot use non-primitive types.

So what is your suggestion for this kind of tests?

I would like to have something like this but I’m not sure if this is the right way and if some testing framework supports this scenario.

[TestData]
public IEnumerable<object> SumTestData()
{
  yield return new { First = 1, Second = 1, Expected = 2 };
  yield return new { First = -1, Second = 1, Expected = 0 };
  yield return new { First = 1, Second = 2, Expected = 3 };
  yield return new { First = 1, Second = -1, Expected = 0 };
}

[TestMethod(DataSource="method:SumTestData")]
public void SumTest(int first, int second, int expected)
{
  // this test is runned for each item that is got from SumTestData method
  // (property -> parameter mapping is no problem)
  ICalculator target = GetSum();
  var actual = target.Sum(first, second);
  Assert.AreEqual(expected, actual);
}

Answer 1

NUnit supports that scenario:

public static IEnumerable SumTestData() {
    return new List<TestCaseData> {
        new TestCaseData( 1,  1,  2),
        new TestCaseData(-1,  1,  0),
        new TestCaseData( 1,  2,  3),
        new TestCaseData( 1, -1,  0)
    };
}

[Test]
[TestCaseSource("SumTestData")]
public void SumTest(int first, int second, int expected) {
}

The parameters can be any type. The TestCaseData constructor takes a param array of objects, so you just have to make sure that your test values are castable to the actual test method parameter types.

Non-void parametrised test method (by @RobertKoritnik)

Upper code can be even further enhanced by having a non void test method and provide results along test data. I also provided an alternative of creating test data method.

public static IEnumerable SumTestData() {
    yield return new TestCaseData( 1,  1).Returns(2);
    yield return new TestCaseData(-1,  1).Returns(0);
    yield return new TestCaseData( 1,  2).Returns(3);
    yield return new TestCaseData( 1, -1).Returns(0);
}

[Test]
[TestCaseSource("SumTestData")]
public int SumTest(int first, int second)
{
    return Sum(first, second);
}