BeEquivalentTo shows enums as decimal in error message

Description

BeEquivalentTo shows enums as decimal in error message

public enum Color
{
    Red,Blue
}

Expected member Color to be 1M, but found 0M.

Complete minimal example reproducing the issue

public enum Color
{
    Red,Blue
}

public class Car
{
    public Color Color { get; set; }
}

[Fact]
public void Test()
{
    var car = new Car
    {
        Color = Color.Red
    };
    car.Should().BeEquivalentTo(new Car() { Color = Color.Blue });
}

Expected behavior:

Message: Expected member Color to be Blue, but found Red.

Actual behavior:

Message: Expected member Color to be 1M, but found 0M.

Versions

• FluentAssertions 5.4.1
• .NET Core 2.0

Additional Information

Running in Xunit, when relevant.

[jnyrup]

Thanks for bringing this up.

The default behavior for comparing enums in BeEquivalentTo is to compare them by value. That is, two (different) enums are considered equivalent if and only if their underlying values are equal.

If you want to compare the enums by name instead, you can use

car.Should().BeEquivalentTo(new Car() { Color = Color.Blue },
    opt => opt.ComparingEnumsByName());

which changes the failure message to

Message: Expected member Color to be "Blue" with a length of 4, but "Red" has a length of 3.

With configuration:
- Use declared types and members
- Compare enums by name
- Match member by name (or throw)
- Without automatic conversion.
- Be strict about the order of items in byte arrays

Getting back to your issue, I think the failure message can be improved for both ComparingEnumsByName and ComparingEnumsByValue.

Some ideas for the failure message:

• Expected member Color to be Color.Blue, but found Color.Red.
• Expected member Color to be Blue (1), but found Red (0).
• Expected member Color to be Color.Blue (1), but found Color.Red (0).

Including more details is useful if one e.g. compares Color.Red = 0 with AnotherColor.Red = 1 by value. Only displaying Message: Expected member Color to be Blue, but found Red. would be confusing.

The relevant class is EnumEqualityStep.

[robvanuden]

Agree, thanks @krajek!