equalWithin on DU types of float

Description

I am building test on discriminated union types that can take on a case =of float=. However the =equalWithin= operator is not able to compare two numbers within a range for such types, making it hard to test things as I need to drill down to perform explicit float conversion. See example:

Repro steps

type myType = | Number of float | Name of string

// inside test:
1.1 * (1. + 2.) |> should (equalWithin 1E-10)  3.3 //this test passes 
(Number (1.1 * (1. + 2.))) |> should (equalWithin 1E-10)  (Number 3.3) //this test fails

Expected behavior

I would like both tests to pass or for there to be a simple way to write the test. Consider example:

let a = //code that produces a record containing myType instances.
a |> should (equalWithin 1E-10) {g="string"; h=Number 4;....}

Currently I have to test field by field so I can perform explicit conversion to floats for the number fields. Maybe the equalWithin operator could be expanded to cover types with declared double fields or similar?

[sergey-tihon]

@CaptnCodr yes, I agree.

That how we write tests in .NET (C#, F#) - multiple assertions for primitive types. If you need more, you can implement helper functions for your project or override equality for record type.

[CaptnCodr]

Hey @johanvts

What simply FsUnit does is:

1. it consumes methods (or are adapted) of specific frameworks (xunit, nunit, mstest) and provides it via operators e.g.: Assert.AreEqual(expected, actual) => actual |> should equal expected
2. it follows that operators are in FsUnit implemented that are real assertions in nunit, xunit and/or mstest
3. there is no “extra logic” implemented only the most necessary to satisfy the operation

equal and equalWithin are very different:

• equal is a simple check: x = y
• equalWithin checks if the actual, expected and tolerance are convertible to float and if the difference between actual and expected is less than the tolerance then this test passes

equal handles all types. equalWithin handles numeral types with a given range (tolerance).

This feature does not fit in FsUnit, the reasons are described above.

I would like to close this issue. Do you agree with it, @sergey-tihon?

Thanks!