Testing character strings using custom classes.

[arangaca]

I've a character vector that uses a custom class foo.

bar <- structure("foo", class = c("foo", "character"))

When comparing this object against the string "foo", the test complains that classes don't match.

test_that("foo", {
  expect_equal(bar, "foo")
})
#> ── Failure (Line 2): foo ───────────────────────────────────────────────────────
#> structure("foo", class = c("foo", "character")) (`actual`) not equal to "foo" (`expected`).
#> 
#> `actual` is an S3 object of class <foo/character>, a character vector
#> `expected` is a character vector ('foo')

I've ended up using the ignore_attr = TRUE parameter in expect_equal() but it's not convenient because I have to use it in many tests (the waldo::compare() doc also recommend not to use it for good reasons).

I've noticed that testing glue strings (classes glue/character) work so there might be a way to make my test work without ignoring attributes.

test_that("foo", {
  expect_equal(glue("foo"), "foo")
})
#> Test passed

How can I make my test pass without ignoring attributes or unclasing the input object?

[Gabor]

If you have many tests like this, then I would write a helper function, that

1. tests the class first,
2. then drops the class and tests the rest with expect_equal().

[arangaca]

Ah yes, forgot to mention it but I was thinking about doing that as well.
Just out of curiosity, why does it work with glue()? Is it because the package uses special constructors from the vctrs package?

[Gabor]

No, glue does not use vctrs, but it does define an S3 method that testthat 3e (waldo) picks up: Add compare_proxy method and convert to testthat 3e · tidyverse/glue@274130c · GitHub