fix #76 by fully qualifying/scoping the httptest function calls in th…

[kforner]

fix #76 by fully qualifying/scoping the httptest function calls in the instrumented code.

Tested locally with my use case: I could use httptest in Suggests: instead of in Depends: in my package and it still works as expected.
And the tests still pass.

[nealrichardson]

Thanks!

Looks like the same issue would occur in httptest2: https://github.com/nealrichardson/httptest2/blob/main/R/capture-requests.R

Would you be willing to make a similar PR over there as well?

[kforner]

Sure. Quick question: Why aren't you using httr builtin callback feature to capture the requests (set_callback()) ?

[nealrichardson]

I don't recall for sure at this point, but the original implementation of httptest predates that feature in httr, so historically that's why it relies on trace(). There may also be a difference in how request errors are handled--I feel like I tried to switch to use the callbacks at some point and ran into an issue.