Remove assert usage from internal/replacer

[DrJosh9000]

Description

Arranging a test I looked at recently to be closer to personal preference.¹ I promise I won't let my feelings get hurt if this PR goes nowhere.

Context

Noticed during recent work.

Changes

Remove assert in favour of stdlib testing plus go-cmp.

Testing

• Tests have run locally (with go test ./...). Buildkite employees may check this if the pipeline has run automatically.
• Code is formatted (with go fmt ./...)

Footnotes

1. https://google.github.io/styleguide/go/decisions#assertion-libraries ↩

[pda]

Do you use an editor snippet or something for this?
It's quite fiddly to type out many times 😅

[pda]

I see https://google.github.io/styleguide/go/decisions#print-diffs doesn't have a strong opinion on the order of (got, want) vs (want, got).

Here's an example from another test I'm trying this style on, where I used the same (got, want) order you've used here:

    env_test.go:44: env.Get() diff (-got +want):
          string(
        -       "intrestng",
        +       "interesting",
          )

To me that diff reads backwards… I'd expect the + to be showing me what it got, as a delta against what it wanted. (Perhaps there's also an argument for the other direction.) I guess I think of the - side of a diff as the older/control side, and the + side as the newer/experiment/work-in-progress side.

I do note that the first (primary?) example in that style guide does use diff (-want +got) which matches what makes sense to me.

Any thoughts?

[DrJosh9000]

Do you use an editor snippet or something for this?
It's quite fiddly to type out many times 😅

I don't, but I should look into using some IDE feature for this. As fiddly as it is to write, I think it pays for itself in time spent writing out.

opinion on the order of (got, want) vs (want, got)

I've seen a few discussions on this as the print-diffs guidance was written 😆 Before it became common, I already had "got before want" drilled into my brain. Someone (I forget who) raised the idea that (-got, +want) is a diff describing "here's what would need to change in the output to match the test", and the original stance (which was to prefer (-want +got)) was weakened to "make the diff direction clear".