dplyr clashes with testthat package when matches is used - r

Question

I am getting an error because testthat::matches clashes with dplyr::matches, and I want to know how to use testthat::test_file to check functions which contain calls to matches(), without having to specify dplyr::matches in the function body.
E.g.:
> testthat::test_file('tmp_fn_testthat_test.R')
Attaching package: ‘testthat’
The following object is masked from ‘package:dplyr’:
matches
The following object is masked from ‘package:purrr’:
is_null
Show Traceback
Rerun with Debug
Error in -matches("tmp") : invalid argument to unary operator In addition: Warning message:
package ‘testthat’ was built under R version 3.2.5
DONE =========================================================================================================================================
This error can be reproduced by saving the following code in a file called tmp_fn_testthat_test.R in your working directory, and running the command testthat::test_file('tmp_fn_testthat_test_20161115.R'). Note that sourcing or running the expect_equal command while testthat is not loaded makes the test pass.
tmp_fn <- function() {
tmp_df <- data.frame(tmp_a = 1, tmp_b = 2)
tmp_df %>%
select(-matches('tmp')) %>%
ncol
}
testthat::expect_equal(tmp_fn(), 0)

Answer 1

This is a known issue with dplyr 0.5. The recommended solution is to use an explicit namespace prefix: dplyr::matches.

Answer 2

A work around appears to be commenting out the library(testthat) in the definition of testthat::test_file, and making function calls explicit (not sure whether this will have bad side effects):
my_test_that_file <- function (path, reporter = "summary", env = testthat::test_env(), start_end_reporter = TRUE,
load_helpers = TRUE)
{
# library(testthat)
reporter <- testthat:::find_reporter(reporter)
if (load_helpers) {
testthat:::source_test_helpers(dirname(path), env = env)
}
lister <- testthat:::ListReporter$new()
if (!is.null(reporter)) {
reporter <- testthat:::MultiReporter$new(reporters = list(reporter,
lister))
}
else {
reporter <- lister
}
testthat::with_reporter(reporter = reporter, start_end_reporter = start_end_reporter,
{
lister$start_file(basename(path))
testthat::source_file(path, new.env(parent = env), chdir = TRUE)
testthat:::end_context()
})
invisible(lister$get_results())
}