Require usage of expect_identical(x, y) where appropriate

This linter enforces the usage of testthat::expect_identical() as the default expectation for comparisons in a testthat suite. expect_true(identical(x, y)) is an equivalent but unadvised method of the same test. Further, testthat::expect_equal() should only be used when expect_identical() is inappropriate, i.e., when x and y need only be numerically equivalent instead of fully identical (in which case, provide the tolerance= argument to expect_equal() explicitly). This also applies when it's inconvenient to check full equality (e.g., names can be ignored, in which case ignore_attr = "names" should be supplied to expect_equal() (or, for 2nd edition, check.attributes = FALSE).

Usage

expect_identical_linter()

Exceptions

The linter allows expect_equal() in three circumstances:

1. A named argument is set (e.g. ignore_attr or tolerance)

2. Comparison is made to an explicit decimal, e.g. expect_equal(x, 1.0) (implicitly setting tolerance)

3. ... is passed (wrapper functions which might set arguments such as ignore_attr or tolerance)

See also

linters for a complete list of linters available in lintr.

Tags

package_development, pkg_testthat

Examples

# will produce lints
lint(
  text = "expect_equal(x, y)",
  linters = expect_identical_linter()
)
#> <text>:1:1: warning: [expect_identical_linter] Use expect_identical(x, y) by default; resort to expect_equal() only when needed, e.g. when setting ignore_attr= or tolerance=.
#> expect_equal(x, y)
#> ^~~~~~~~~~~~~~~~~~

lint(
  text = "expect_true(identical(x, y))",
  linters = expect_identical_linter()
)
#> <text>:1:1: warning: [expect_identical_linter] Use expect_identical(x, y) by default; resort to expect_equal() only when needed, e.g. when setting ignore_attr= or tolerance=.
#> expect_true(identical(x, y))
#> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~

# okay
lint(
  text = "expect_identical(x, y)",
  linters = expect_identical_linter()
)
#> ℹ No lints found.

lint(
  text = "expect_equal(x, y, check.attributes = FALSE)",
  linters = expect_identical_linter()
)
#> ℹ No lints found.

lint(
  text = "expect_equal(x, y, tolerance = 1e-6)",
  linters = expect_identical_linter()
)
#> ℹ No lints found.