How to compare lists using fluent-assertions?

Question

I want to compare a list of objects, ignoring the order of the objects in the list and only comparing some of the properties in the objects, currently I'm using the following code to perform this comparison:

actual.Should().NotBeNull();
actual.Count.Should().Be(expected.Count);
//compare ignoring order
foreach (var exp in expected)
    actual.Should().Contain(act =>
        act.IndividualId.Equals(exp.IndividualId)
        && act.Email.Equals(exp.Email)
        && act.FirstName.Equals(exp.FirstName)
        && act.LastName.Equals(exp.LastName)
    );

However this seems less than ideal, as when there is a failure you do not get a print out of the expected values. Is there a built in mechanism for performing this comparison using fluent assertions?

Kanpur

Answer 1

Not right now. We do have the new equivalency assertion syntax of FA 2.0, but that will also verify if the objects appear in the right order. For FA 2.1 I'm trying to support that, but I'm not sure yet if that will work. It basically means it has to compare the entire object graph behind a collection item with the object graphs for each and every other item in the collection. Surely it will be rather slow.

Sheaves

Is it possible say compare two List<string> types using actual.Should().Contain(expected)? – Percyperdido

Yes, you can do actual.Should().BeEquivalentTo(expected); – Sheaves

for flexibility we usually serialize each object to json then use string compare, the error output looks good to and you never need to update your unit test if someone adds a new property – Dhar

@DennisDoomen, Are there any new approaches in the current FA? – Unstudied

In version 2.1 of FA we started to ignore ordering of items by default. Is that what you mean? – Sheaves

Answer 2

In order to assert that a collection of objects is equivalent to another collection of objects, e.g. comparing two List<T>, you can use the BeEquivalentTo() method:

collection.Should().BeEquivalentTo(expectedResult);

Here, I'm using the FluentAssertions nuget package.

Feodora

This only works when the two Lists are in the same other.... – Tapley

@IfeoluwaOsungade According to the documentation, BeEquivalentTo does not check the order: fluentassertions.com/objectgraphs/#ordering My own experience confirms that. – Jessikajessup