FluentAssertions factor out repeated config

Question

I have unit-test code like this:

// version3 should be a copy of version2 with some differences
version3.Data.ShouldBeEquivalentTo(version2,
  option => option
    .Excluding(x => x.Id)
    .Excluding(x => x.Status)
    .Excluding(x => x.Stale)
    .Excluding(x => x.Body)
    .Excluding(x => x.CreatedBy)
    .Excluding(x => x.UpdatedBy),
  "because version3 is version2 updated");

And then again

// version4 should be a copy of version3 with some differences
version4.Data.ShouldBeEquivalentTo(version3,
  option => option
    .Excluding(x => x.Id)
    .Excluding(x => x.Status)
    .Excluding(x => x.Stale)
    .Excluding(x => x.Body)
    .Excluding(x => x.CreatedBy)
    .Excluding(x => x.UpdatedBy),
  "because version4 is version3 updated");

How can I factor option out?

I would like to make something like this:

// version3 should be a copy of version2 with some differences
version3.Data.ShouldBeEquivalentTo(version2,
  option => baseOption,
  "because version3 is version2 updated");

And maybe even this:

// version3 should be a copy of version2 with some differences
version3.Data.ShouldBeEquivalentTo(version2,
  option => baseOption
    .Excluding(x => x.OtherProperty),
  "because version3 is version2 updated");

declare the delegate external to the method call and append to it as needed. — Nkosi, May 04 '18 at 02:33
Can you please provide an example. I haven't had much luck with that. — Jevon Kendon, May 04 '18 at 02:36

score 4 · Accepted Answer · answered May 04 '18 at 02:53

Declare the option delegate externally as the base

Func<FluentAssertions.Equivalency.EquivalencyAssertionOptions<MyDataType>,
    FluentAssertions.Equivalency.EquivalencyAssertionOptions<MyDataType>>
    baseOption = option => option
        .Excluding(x => x.Id)
        .Excluding(x => x.Status);

And use it with the assertion

// version3 should be a copy of version2 with some differences
version3.Data.ShouldBeEquivalentTo(version2, baseOption, 
    "because version3 is version2 updated");

For other assertion that needs to build upon the base you have to invoke the delegate and append additional options

// version3 should be a copy of version2 with some differences
version3.Data.ShouldBeEquivalentTo(version2,
  option => baseOption(option)
    .Excluding(x => x.OtherProperty),
  "because version3 is version2 updated");

You should note that the current syntax being used has been deprecated in newer versions of the framework.

version3.Should().BeEquivalentTo(version2, baseOption, 
    "because version3 is version2 updated");

score 2 · Answer 2 · answered May 04 '18 at 05:00

2

Or switch to v5 so you compare your subject-under-test against an anonymous type where you only define the properties you care about for that particular test.

answered May 04 '18 at 05:00

Dennis Doomen

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1

This feature simplified a lot of test cases. – Fabio May 04 '18 at 06:23

FluentAssertions factor out repeated config

2 Answers2