Block obvious "yoda tests"

Yoda tests use (expected, actual) instead of the more common (actual, expected). This is not always possible to detect statically; this linter focuses on the simple case of testing an expression against a literal value, e.g. (1L, foo(x)) should be (foo(x), 1L).

Usage

yoda_test_linter()

See also

linters for a complete list of linters available in lintr. https://en.wikipedia.org/wiki/Yoda_conditions

Tags

best_practices, package_development, pkg_testthat, readability

Examples

# will produce lints
lint(
  text = "expect_equal(2, x)",
  linters = yoda_test_linter()
)
#> <text>:1:1: warning: [yoda_test_linter] Compare objects in tests in the order 'actual', 'expected', not the reverse. For example, do expect_equal(foo(x), 2L) instead of expect_equal(2L, foo(x)).
#> expect_equal(2, x)
#> ^~~~~~~~~~~~~~~~~~

lint(
  text = 'expect_identical("a", x)',
  linters = yoda_test_linter()
)
#> <text>:1:1: warning: [yoda_test_linter] Compare objects in tests in the order 'actual', 'expected', not the reverse. For example, do expect_identical(foo(x), 2L) instead of expect_identical(2L, foo(x)).
#> expect_identical("a", x)
#> ^~~~~~~~~~~~~~~~~~~~~~~~

# okay
lint(
  text = "expect_equal(x, 2)",
  linters = yoda_test_linter()
)
#> ℹ No lints found.

lint(
  text = 'expect_identical(x, "a")',
  linters = yoda_test_linter()
)
#> ℹ No lints found.