[aesthesia]

How is that ambiguous? The best interpretation I can find where "test" is a verb is an elision: Test [that] B is an alternative to test A. That is an unlikely reading: "test" is a verb in the first instance and a noun in the second, breaking parallelism. And it's just a very unlikely thing to direct someone to do.

[summarity]

"Test B is an alternative to test A."

could mean there's a Test B and a Test A, and they're interchangeable.

Or:

You can run Test B to confirm A works, that is "to test A".

Again the stated goal to clear documentation for non-native or limited-exposure speakers. This doesn't pass that test.

[aesthesia]

Ah, I see, taking "to test A" as an infinitive. But it would be strange to say test B is an alternative without saying what it's an alternative to. The other reading still seems quite unlikely.

[dymk]

The point of STE100 is to avoid ambiguity like this, though.

[thomascountz]

The point of STE is to support technical writers who have knowledge of the matter and a style guide. In other words, STE will not make something unambiguous simply by replacing words. The example sentence is just to illustrate a grammar rule: "test" as a verb vs a noun. That is all. You should not assume an STE rule will disambiguate a single sentence pulled out of context.