c# - 在 NUnit 中，如何为结构的属性比较指定容差？

Question

我有以下 NUnit 测试，由于某种原因结构比较失败:

public struct Record
{
    public double P1 { get; set; }
    public double P2 { get; set; }
}

[TestFixture]
public class UnitTest
{
    [Test]
    public void PassingTest()
    {
        Assert.That(100, Is.EqualTo(99.99999999).Within(.0001));
    }

    [Test]
    public void FailingTest()
    {
        Assert.That(new Record { P1 = 1.0, P2 = 100 },
            Is.EqualTo(new Record { P1 = 1.0, P2 = 99.99999999 }).Within(.0001));
    }

    [Test]
    public void AlsoPassesTest()
    {
        Assert.That(new Record { P1 = 1.0, P2 = 100 },
            Is.EqualTo(new Record { P1 = 1.0, P2 = 100 }).Within(.0001));
    }
}

问题(1):为什么structs comparison的测试会失败？问题 (2):如果结构比较测试失败是因为没有“深入”应用容差，我该如何设置才能通过结构比较测试？

Answer 1

看来你必须手写这个。像这样:

static class IsAlternatively
{
  public static AlternativeEqualConstraint EqualTo(Record r)
  {
    return new AlternativeEqualConstraint(r);
  }
}

class AlternativeEqualConstraint : NUnit.Framework.Constraints.Constraint
{
  readonly Record expected;
  double tolerance;

  public AlternativeEqualConstraint(Record r)
  {
    this.expected = r;
  }

  public AlternativeEqualConstraint Within(double tolerance)
  {
    this.tolerance = tolerance;
    return this;
  }


  public override bool Matches(object obj)
  {
    actual = obj;

    if (!(obj is Record))
      return false;

    var other = (Record)obj;

    return Math.Abs(other.P1 - expected.P1) < tolerance && Math.Abs(other.P2 - expected.P2) < tolerance;
  }

  public override void WriteDescriptionTo(NUnit.Framework.Constraints.MessageWriter writer)
  {
    writer.WriteExpectedValue(expected);
    writer.WriteMessageLine("Expected within tolerance '{0}'.", tolerance);
  }

  public override void WriteActualValueTo(NUnit.Framework.Constraints.MessageWriter writer)
  {
    writer.WriteActualValue(actual);
  }
}

当然可以这样使用:

  Assert.That(new Record { P1 = 1.0, P2 = 100.0, },
    IsAlternatively.EqualTo(new Record { P1 = 1.0, P2 = 99.99999999, }).Within(.0001)
    );

  Assert.That(new Record { P1 = 1.0, P2 = 100.0, },
    IsAlternatively.EqualTo(new Record { P1 = 1.0, P2 = 100.0, }).Within(.0001)
    );

  Assert.That(new Record { P1 = 1.0, P2 = 100.0, },
    IsAlternatively.EqualTo(new Record { P1 = 1.0, P2 = 66.6, }).Within(.0001)
    );