CODEWITHSUNDEEP
c#unit-testingnunit
Jordi
Jordi

Reputation: 2567

NUnit check a call does not throw using fluent assertions

I developed an extension method with the signature void ThrowIfAny<T>(this IEnumerable<T> e, Func<T, bool> f) and I'm unit testing it. Logically, one of the tests is to check that does not throw. I know that I can write this assert like this:

Assert.DoesNotThrow(() => anEnum.ThrowIfAny(t => false));

However, I'm using constraint based assertions for the rest of my unit tests, and I'd like to know if this assert can be written using this style, maybe something like this (it doesn't compile):

Assert.That(() => anEnum.ThrowIfAny(t => false), Does.Not.Throw);

Upvotes: 1

Views: 615

Answers (2)

rjnilsson
rjnilsson

Reputation: 2343

This should do it:

Assert.That(() => anEnum.ThrowIfAny(t => false), Throws.Nothing);

See ThrowsNothingContraint.

Upvotes: 4

eocron
eocron

Reputation: 7546

You basically need to write extensions that help you do this. I usually write multiple Assert extensions using CAssert name:

public static class CAssert
{
    public static void That(Action action, MyTestSuit suit)
    {
        try
        {
            action();
            if(suit.ShouldThrow)
            {
                Assert.Fail("Not thrown any exception but expected to.")
            }
        }
        catch(Exception e)
        {
            if(suit.ShouldNotThrow)
            {
                Assert.Fail("Exception was thrown but not expected.")
            }
        }
    }
}

Test suits is basically a set of options. It is mostly singletons. You can overload it's operators however you like, for example to combine options from different suits:

CAssert.That(()=> 1/0, Throws.Error<DivideByZeroException>() | Throws.Error<ArithmeticException>());

Upvotes: 0

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