Home > R > Automatically convert RUnit tests to testthat tests

Automatically convert RUnit tests to testthat tests

There’s a new version of my assertive package, for sanity-checking code, on its way to CRAN. The release has been delayed a while, since my previous attempt at an upload met with an error that was only generated on the CRAN machine, but not on my own. The problem lay with some code designed to autorun the RUnit tests for the package. After fiddling for a while and getting nowhere, I decided it was time to make the switch to testthat.

I’ve been a long-time RUnit user, since the syntax is near-identical to every other xUnit variant in every programming language. So switching between RUnit and MATLAB xUnit or NUnit requires no thinking. testthat has a couple of important advantages over RUnit though.

test_package makes it easy to, ahem, test your package. A page of code for finding and nicely displaying bad tests has been reduced to test_package("assertive").

Secondly, testing for warnings is much cleaner. In RUnit, you have to use convoluted mechanisms like:

test.sqrt.negative_numbers.throws_a_warning <- function()
{
  old_ops <- options(warn = 2)
  on.exit(options(old_ops))
  checkException(sqrt(-1))
}

The testthat equivalent is more readable:

test_that(
  "sqrt throws a warning for negative number inputs",
  {
    expect_warning(sqrt(-1))
  }
)

Thirdly, testthat caches tests, so you spend less time waiting for tests that you know are fine to rerun.

These benefits mean that I’ve been meaning to switch packages for a while. The big problem was that the assertive package contains over 300 unit tests. At about a minute or so to update each tests, that was five hours of tedious work that I couldn’t be bothered to do. Instead, I spent two days making a package that automatically converts RUnit tests to testthat tests. Not exactly a time saving, but it was more fun.

It isn’t on CRAN yet, but you can get it from github.

library(devtools)
install_github("richierocks/runittotestthat")

The package contains functions to convert tests on an individual/file/package basis.

convert_test takes an RUnit test function and returns a call to test_that. Here’s an example for the sqrt function.

library(runittotestthat)
test.sqrt.3.returns_1.732 <- function()
{
  x <- 3
  expected <- 1.73205080756888
  checkEquals(sqrt(x), expected)
}
convert_test(test.sqrt.3.returns_1.732)
## test_that("test.sqrt.3.returns_1.732", {
##   x <- 3
##   expected <- 1.73205080756888
##   expect_equal(expected, sqrt(x))
## })

convert_test works with more complicated test functions. You can have multiple checks, nested inside if blocks or loops if you really want.

test.some_complicated_nonsense.returns_an_appropriate_testthat_test <- function()
{
  x <- 6:10
  for(i in 1:5)
  {
    if(i %% 2 == 0)
    {
      checkTrue(all(x > i), msg = "i divisible by 2") 
      if(i == 4)
      {
        checkIdentical(4, i, msg = "i = 4")
      } else
      {
        while(i > 0) 
        {
          checkIdentical(2, i, msg = "i = 2")
        }
        repeat
        {
          checkException(stop("!!!"))
          break
        }
      }
    }               
  }
}
convert_test(test.some_complicated_nonsense.returns_an_appropriate_testthat_test)
## test_that("test.some_complicated_nonsense.returns_an_appropriate_testthat_test", 
## {
##   x <- 6:10
##   for (i in 1:5) {
##     if (i%%2 == 0) {
##       expect_true(all(x > i), info = "i divisible by 2")
##       if (i == 4) {
##         expect_identical(i, 4, info = "i = 4")
##       }
##       else {
##         while (i > 0) {
##           expect_identical(i, 2, info = "i = 2")
##         }
##         repeat {
##           expect_error(stop("!!!"))
##           break
##         }
##       }
##     }
##   }
## })

Of course, the main use for this is converting whole files or packages at at time, so runittotestthat contains convert_test_file and convert_package_tests for this purpose. By default (so you don’t overwrite your RUnit tests by mistake), they write their output to the console, but you can also write the resulting testthat tests to a file. converting all 300 of assertive’s tests was as easy as

convert_package_tests(
  "assertive", 
  test_file_regexp = "^test", 
  testthat_files = paste("new-", runit_files)
)

In that line of code, the runit_files variable is a special name that refers to the names of the files that contain you RUnit tests. It means that the output testthat file names can be be based upon original input names.

Although runittotestthat works fine on all my tests, automatic code editing is a tricky task, so there may be some weird edge cases that I’ve missed. Please download the package and play with it, and let me know if you find any bugs.

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