Reduce nesting in tests by using withr::local_envvar()

[olivroy]

#589 (comment)

Does something along this make sense @hadley ?

Note: easier to review if selecting hide whitespace in github https://github.com/r-lib/covr/pull/599/files?diff=unified&w=1

[hadley]

I was expecting something more like this:

test_that("it generates a properly formatted json file", {
  withr::local_envvar(ci_vars)
  local_mocked_bindings(
    RETRY = function(...) list(...),
    content = identity,
    local_branch = function(dir) "master",
    current_commit = function(dir) "a94a8fe5ccb19ba61c4c0873d391e987982fbbd3"
  )

  res <- codecov(coverage = cov)
  json <- jsonlite::fromJSON(res$body)

  expect_match(json$files$name, "R/TestS4.R")
  expect_equal(
    json$files$coverage[[1]],
    c(
      NA, NA, NA, NA, NA, NA, NA, 5, 2, NA, 3, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA,
      NA, NA, NA, NA, 1, NA, NA, NA, NA, NA, 1, NA, NA, NA, NA, NA, 1, NA
    )
  )
  expect_equal(json$uploader, "R")
})

[hadley]

I'd suggest you keep this closer to its original position to make the diff a little simpler.

[jimhester]

Looks good, thanks for working on this @olivroy and @hadley for the review!