Require usage of expect_false(x) over expect_true(!x)

testthat::expect_false() exists specifically for testing that an output is FALSE. testthat::expect_true() can also be used for such tests by negating the output, but it is better to use the tailored function instead. The reverse is also true – use expect_false(A) instead of expect_true(!A).

Usage

expect_not_linter()

See also

linters for a complete list of linters available in lintr.

Tags

best_practices, package_development, pkg_testthat, readability

Examples

# will produce lints
lint(
  text = "expect_true(!x)",
  linters = expect_not_linter()
)
#> <text>:1:1: warning: [expect_not_linter] expect_false(x) is better than expect_true(!x), and vice versa.
#> expect_true(!x)
#> ^~~~~~~~~~~~~~~

# okay
lint(
  text = "expect_false(x)",
  linters = expect_not_linter()
)
#> ℹ No lints found.