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wiki: CodeReviewComments should more thoroughly describe test helper functions #30246

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posener opened this issue Feb 15, 2019 · 3 comments
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@posener
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@posener posener commented Feb 15, 2019

The document already covers testing helper functions, and how to use them. I propose to add instructions how to write testing helper functions. Two things that I thought of are:

  1. The first argument should always be t *testing.T.
  2. The first line of the function should be t.Helper().

The reason for this issue is that currently context is instructed to be the first argument of a function. A testing helper function that I wrote testCtx(t *testing.T, ctx context.Context) result in a lint warning - context should always be the first argument. I opened golang/lint#422 and created a fix golang/lint#423, but it was declined for the reason that lint enforces only what's in EffectiveGo and CodeReviewComments.

The current state is that if I want to have this function I should declare it as testCtx(ctx context.Context, t *testing.T) which fills wrong to me.

@bcmills
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@bcmills bcmills commented Feb 15, 2019

2. The first line of the function should be t.Helper().

That isn't necessarily the case: sometimes you really do want to report line numbers from inside the helper-function rather than outside. (It largely depends on whether the function is implementing the body of the test, or just doing a bit of opaque setup.)

@katiehockman katiehockman changed the title wiki: CodeReviewComments: Add instructions for test helper functions wiki: CodeReviewComments should describe test helper function arguments Feb 15, 2019
@katiehockman katiehockman changed the title wiki: CodeReviewComments should describe test helper function arguments wiki: CodeReviewComments should more thoroughly describe test helper functions Feb 15, 2019
@katiehockman
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@katiehockman katiehockman commented Feb 15, 2019

  1. The first argument should always be t *testing.T.

I'm also not convinced of this one. The documentation for context indicates that context should almost always be the first argument. I interpret the "almost" to mean that the cases where you use a newly created context in the body of the function, rather than as a function param, are pretty rare. Not to mean there are cases where you pass a context as anything other than the first param. It is also a rare case that a test would need both the context and t *testing.T, so adding that contingency seems superfluous. The linter always expecting that context be the first argument seems preferable to me.

@smu-ggl
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@smu-ggl smu-ggl commented Feb 25, 2020

I find it pretty confusing to have lots of functions in tests that don't take a context.Context read as
func a (t *testing.T,...)
func b (t *testing.T,...)
And then have the outlier that uses a context (whether it is needed to run the test or be under test) read
func c(ctc context.Context, t *testing.T, ...)
I need to re-adjust my reading and instead of just kind of acknowledging the presence of testing.T, I actually need to think about it.
To me, having the "almost always" part interpreted as "with exceptions, one of them being functions in tests that take a testing.T argument" would be preferable.

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