C#, NUnit: Is it possible to test that a DateTime is very close, but not necessarily equal, to another

cdatetimenunitunit testing

Say I have this test:

[Test]
public void SomeTest()
{
    var message = new Thing("foobar");
    Assert.That(thing.Created, Is.EqualTo(DateTime.Now));
}

This could for example fail the constructor of Thing took a bit of time. Is there some sort of NUnit construct that would allow me to specify that the Created time don't have to be exactly equal to DateTime.Now, as long as it for example is within one second of it?

And yes I know constructors are not supposed to take much time, but just as an example :p

Best Answer

I haven't tried it, but according to the docs it looks like this should work:

Assert.That(thing.Created, Is.EqualTo(DateTime.Now).Within(1).Minutes);

I can't say I'm normally much of a fan of the constraints system - I'm an Assert.AreEqual fan - but that particular construct is rather neat.

(As a point of principle I should remark that you'd be best off passing some sort of "clock" interface in as a dependency, and then you wouldn't have any inaccuracy. You could fake it for the tests, and use the system clock for production.)

Related Solutions

How to ignore a test based on another test in NUnit

NUnit supports an "Assume.That" syntax for validating setup.This is documented as part of the Theory (thanks clairestreb). In the NUnit.Framework namespace is a class Assume. To quote the documentation:

/// Provides static methods to express the assumptions
/// that must be met for a test to give a meaningful
/// result. If an assumption is not met, the test
/// should produce an inconclusive result.

So in context:

public void TestGet() {
    MyList sut = new MyList()
    Object expecting = new Object();
    sut.Put(expecting);
    Assume.That(sut.size(), Is(1));
    Assert.That(sut.Get(), Is(expecting));
}

.net – NUnit, is it possible to continue executing test after Assert fails

I prefer to be practical and put several related assertions in one method.

I have a helper class which enables the following syntax (I use):

AssertAll.Succeed(
    () => Assert.AreEqual("bb", id.Context),
    () => Assert.AreEqual("abc", id.FullName),
    () => Assert.AreEqual("b", id.SessionID));

which gives me error messages like this:

Assert.AreEqual failed. Expected:<bb>. Actual:<b\c>. 
Assert.AreEqual failed. Expected:<abc>. Actual:<[b\c]a{103}>. 
at FXP_COM.Tests.EnumToStringConverterterTests.<>c__DisplayClass3.<ShouldConvert>b__0() in UnitTest1.cs: line 31
at FXP_COM.Tests.AssertAll.Succeed(Action[] assertions) in UnitTest1.cs: line 46 at FXP_COM.Tests.AssertAll.Succeed(Action[] assertions) in UnitTest1.cs: line 62
at FXP_COM.Tests.EnumToStringConverterterTests.ShouldConvert() in UnitTest1.cs: line 30

and the helper class is the following:

using System;
using NUnit.Framework;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;

public static class AssertAll
{
    public static void Succeed(params Action[] assertions)
    {
        var errors = new List<Exception>();

        foreach (var assertion in assertions)
            try
            {
                assertion();
            }
            catch (Exception ex)
            {
                errors.Add(ex);
            }

        if (errors.Any())
        {
            var ex = new AssertionException(
                string.Join(Environment.NewLine, errors.Select(e => e.Message)),
                errors.First());

            // Use stack trace from the first exception to ensure first
            // failed Assert is one click away
            ReplaceStackTrace(ex, errors.First().StackTrace);

            throw ex;
        }
    }

    static void ReplaceStackTrace(Exception exception, string stackTrace)
    {
        var remoteStackTraceString = typeof(Exception)
            .GetField("_remoteStackTraceString",
                BindingFlags.Instance | BindingFlags.NonPublic);

        remoteStackTraceString.SetValue(exception, stackTrace);
    }
}

Best Answer

Related Solutions

How to ignore a test based on another test in NUnit

.net – NUnit, is it possible to continue executing test after Assert fails

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