Require usage of expect_s3_class()

testthat::expect_s3_class() exists specifically for testing the class of S3 objects. testthat::expect_equal(), testthat::expect_identical(), and testthat::expect_true() can also be used for such tests, but it is better to use the tailored function instead.

Usage

expect_s3_class_linter()

See also

• linters for a complete list of linters available in lintr.

• expect_s4_class_linter()

Tags

best_practices, package_development, pkg_testthat

Examples

# will produce lints
lint(
  text = 'expect_equal(class(x), "data.frame")',
  linters = expect_s3_class_linter()
)
#> <text>:1:1: warning: [expect_s3_class_linter] expect_s3_class(x, k) is better than expect_equal(class(x), k). Note also expect_s4_class() available for testing S4 objects.
#> expect_equal(class(x), "data.frame")
#> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

lint(
  text = 'expect_equal(class(x), "numeric")',
  linters = expect_s3_class_linter()
)
#> <text>:1:1: warning: [expect_s3_class_linter] expect_s3_class(x, k) is better than expect_equal(class(x), k). Note also expect_s4_class() available for testing S4 objects.
#> expect_equal(class(x), "numeric")
#> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

# okay
lint(
  text = 'expect_s3_class(x, "data.frame")',
  linters = expect_s3_class_linter()
)
#> ℹ No lints found.

lint(
  text = 'expect_type(x, "double")',
  linters = expect_s3_class_linter()
)
#> ℹ No lints found.