pedrofgd/xunit-test-practice

Learning the xUnit.net test framework

Practicing unit tests with xUnit

Resume:

• sut: System Under Test
• Each test is running in their own instance of the class
• Theory and InlineData() decorators
• Skip property ([Fact(Skip = "This test is broken")])
• MemberData(nameof()) decorator
• ClassData(typeof()) decorator
• Collections

Using Theory to don't repeat code

For tets the same thing but with different values, like Add two positive numbers and then two negative numbers:

  [Theory]
  [InlineData(13, 5, 8)]
  [InlineData(0, -5, 5)]
  [InlineData(0, 0, 0)]
  public void AddTwoNumbersShouldEqualTheirEqualTheory(
    decimal expected, decimal firstToAdd, decimal secondToAdd
  )
  {
    _sut.Add(firstToAdd);
    _sut.Add(secondToAdd);
    Assert.Equal(expected, _sut.Value);
  }

Get the input more complex

  public static IEnumerable<object[]> TestData()
  {
    yield return new object[](15, new decimal[]{ 10, 5 });
    yield return new object[](15, new decimal[]{ 5, 5, 5 });
    yield return new object[](-10, new decimal[]{ -30, 20 });
  }

And then, in the tets method, use the MemberData decorator:

  [Theory]
  [MemberData(nameof(TestData))]
  public void AddManyNumbersShouldEqualTheirEqualTheory(
    decimal expected, params decimal[] valuesToAdd)
  {
    foreach (var value in valuesToAdd)
    {
      _sut.Add(value);
    }

    Assert.Equal(expected, _sut.Value);
  }

Other way to do that is using a class:

public class DivisionTestData : IEnumerable<object[]>
{
  public IEnumerator<object[]> GetEnumerator()
  {
    yield return new object[] {30, new decimal[] { 60, 2 }};
    yield return new object[] {1, new decimal[] { 30, 30 }};
    yield return new object[] {0, new decimal[] { 0, 30 }};
  }

  IEnumerator IEnumerable.GetEnumerator()
  {
    return GetEnumerator();
  }
}

The method keeps like when using MemberData, going through the object[]. The only change in this case is the decorator ClassData(typeof()).

Behavior of xUnit

By default, xUnit run all tests in paralel.

For change that behavior, use an override class method of the own xUnit:

using Xunit;

[assembly: CollectionBehavior(DisableTestParallelization = true)]

Collections

We can use collections to run many tests using the same context.

• [CollectionDefinition("name")]
• public class GuidGeneratorDefinition : ICollectionFixture<GuidGenerator> {}
• [Collection("name")]

This is really important for integrated tests.