Possibility of accepting an interface instead of testing.T

[hrtkpf]

What do you want to see?

Hello,

we have implemented a custom struct that embeds *testing.T and adds some internal functionality, but does not change the interface.

Our custom struct looks something like this:

type Custom struct {
	*testing.T
}

func (t *Custom) Errorf(format string, args ...any) {
	// Some custom functionality here

	t.T.Errorf(format, args...)
}

Using that custom struct with e2e-framework, however, is a bit difficult because funcs like Test in the Environment interface (see here) require a concrete *testing.T type instead of an interface.

Would it be possible to accept an interface instead, like testing.TB? Are there specific reasons why the concrete type was chosen instead of an interface? For reference, testify even has an own interface, which makes using custom wrappers like ours straightforward to use.

Thank you!

Extra Labels

No response

[varnastadeus]

Have same use case

[vladimirvivien]

@hrtkpf, Thank you for pointing this out. Using *testing.T was an early design decision that worked Okay until you pointed out your issue. Using an interface (i.e. testing.TB) as you suggested would be a major design change that could break the API. However, I think it's worth further investigation to see how this could be done with minimum disruption to the existing API.

[harshanarayana]

+1 to what @vladimirvivien mentioned. I did a few quick checks and made a small prototype but adding this with keeping backward compatibility is proving to be really painful.

One Option I could think of was to add a series of new methods/helper functions that provides the ability to accepting the interface over the *testing.T. Would that be a good thing to do? @vladimirvivien

[harshanarayana]

@vladimirvivien any suggestions ?

[vladimirvivien]

Apologies for the delay - @harshanarayana and @hrtkpf .
Avoiding breaking backward compat is paramount. Nevertheless, this may be an opportunity to reimagine how certain portion of the API could evolve to support this. @harshanarayana if you have something you are thinking about, paste it here. I will give this some thought as well.