CODEWITHSUNDEEP
c#unit-testingnunitdefaultfluent-assertions
Marcel
Marcel

Reputation: 15742

How to assert a default value of a property with FluentAssertions?

I have a class with some fields/properties etc., of various types:

public string SomeStringData;
public int? SomeNullableIntegerData;
public SomeDataClass SomeSpecificData;
public int SomeIntegerData;

In part of my code, only the SomeStringData should be filled, and I want to test explicitly that. I use FluentAssertions and have

actual.SomeStringData.Should().Be("Whatever");

But how to test, that none of the other elements are not touched and still have their default value? I could, of course:

actual.SomeNullableIntegerData.Should().NotHaveValue("Must have no value.");
actual.SomeDataClass.Should().BeNull("Must have no value.");
actual.SomeNullableIntegerData.Should().Be(0, "Must have no value.");

But, how to express more clearly that these items should have the default value?

Like for example with an imaginary BeDefault operator:

actual.SomeNullableIntegerData.Should().BeDefault("Must have no value.");
actual.SomeDataClass.Should().BeDefault("Must have no value.");
actual.SomeNullableIntegerData.Should().BeDefault("Must have no value.");

Are there such options?

Upvotes: 3

Views: 3924

Answers (2)

Sergey Berezovskiy
Sergey Berezovskiy

Reputation: 236318

I would create extension method 

public static void ShouldHaveDefaultValue<T>(this T value)
{
    if (!EqualityComparer<T>.Default.Equals(value, default(T)))
        throw new AssertionException("Must have default value.");
}

Usage:

actual.SomeNullableIntegerData.ShouldHaveDefaultValue();
actual.SomeDataClass.ShouldHaveDefaultValue();
actual.SomeIntegerData.ShouldHaveDefaultValue();

Extending Should() with BeDefault() would be difficult, because there is different Should() extensions which return different assertions objects - BooleanAssertions, StringAssertions, GuidAssertions etc. And all this assertions classes don't have common base class you would be able to extent.

Upvotes: 4

Dennis Doomen
Dennis Doomen

Reputation: 8909

I would just capture the previous values upfront and assert that after executing whatever is supposed to make the change, those values still have their default values. That proposed BeDefault method can never make any assumptions about a 'default'.

Upvotes: 0

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