About

This package was created as an example for using covr together with shinytest It also contains template instructions for both Docker and Travis CI.

Explanation

Covr works by adding instrumentation to code. This instrumentation records whenever a line is executed. When R exits, the instrumentation results are stored in a file. This file is afterwards read and converted into an HTML report (or uploaded to an external site).

When using covr in combination with shinytest, two problems arise:

1. Shinytest launches a separate process, which loads all code from scratch. Covr instrumentation is then lost.
2. Furthermore, Shiny terminates non-gracefully, not allowing covr to write out coverage results.

The solution to the first problem is to instrument code manually in the R Shiny process, as @jimhester (https://github.com/r-lib/covr/issues/277)[suggested]:

  registerShinyDebugHook <<- function(params) {
    covr:::replace(covr:::replacement(params$name, env = params$where))
  }

This is not needed when the code is in an R package. When using covr::package_coverage, the R package is installed in a temporary directory and instrumentation is added when the package is loaded. As long as this package version is used by the Shiny process (see tests/testthat/test-shinyTest.R), instrumentation is in place. I have added some small extra code to ensure the package under test is always installed as a package. This is required because shinytest launches an external package; any code loaded by devtools::load_all() will not be available...

The second problem can be easily solved by terminating Shiny gracefully (see tests/shinyTest/tests/test.R).

p <- app$.__enclos_env__$private$shinyProcess
p$interrupt()
p$wait()

Improvements

• In my view, a subprocess launched during testing should also have access to the code. Perhaps the subprocess should also use devtools::load_all()?
• It is easy to forget to gracefully close the Shiny process in shinytest