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)
.
See also
linters for a complete list of linters available in lintr. https://en.wikipedia.org/wiki/Yoda_conditions
Examples
# will produce lints
lint(
text = "expect_equal(2, x)",
linters = yoda_test_linter()
)
#> ::warning file=<text>,line=1,col=1::file=<text>,line=1,col=1,[yoda_test_linter] Tests should compare objects in the order 'actual', 'expected', not the reverse. For example, do expect_equal(foo(x), 2L) instead of expect_equal(2L, foo(x)).
lint(
text = 'expect_identical("a", x)',
linters = yoda_test_linter()
)
#> ::warning file=<text>,line=1,col=1::file=<text>,line=1,col=1,[yoda_test_linter] Tests should compare objects in the order 'actual', 'expected', not the reverse. For example, do expect_identical(foo(x), 2L) instead of expect_identical(2L, foo(x)).
# okay
lint(
text = "expect_equal(x, 2)",
linters = yoda_test_linter()
)
lint(
text = 'expect_identical(x, "a")',
linters = yoda_test_linter()
)