Extensibility issues and unit testing support of custom converters

[niklas-holma]

To support verification of our own datatype responses I wrote some custom converters (inheriting WriteOnlyJsonConverter<>). To test them I could write some tests using verify, but in this case I wanted to test only parts of the serialization plus to avoid any file operations overhead. My conclusions are that its impossible (?) since a the internals of Verify are so tightly integrated, here are some of the approaches i tried and impediments i came across:

• Approach: Trying to create a VerifyJsonWriter in the test calling write methods on the converter directly.

  • The constructor of the VerifyJsonWriter is internal, making it impossible to create statically.
  • The Counter.Current is AsyncLocal and as such will only work when Verify uses it.

• Approach: Trying to call JsonFormatter .ToJson()

  • Although the .ToJson method is public, its unaccessable since the JsonFormatter class is internal.

• Approach: Trying to call Argon.JsonConvert.SerializeObject with the converter configured

  • Exception is thrown when the base class is trying to runtime cast the writer object to a VerifyJsonWriter (false interface).

Improvement suggestions

• Make interfaces for VerifyJsonWriter (and similar classes)
• New method Verifier.SerializeOnly that returns the serialized target as verify would use it, without the file and diffing workflow involved.
• Documentation of best practice on how to unit test custom converters.

[SimonCropp]

this is in 30.8.0 https://github.com/VerifyTests/Verify/blob/main/docs/serializer-settings.md#testing-jsonconverters

thoughts?

[niklas-holma]

That was quick! These changes seems to solve my issue 👍

[SimonCropp]

good to hear.

let me know if you need any tweaks