Allow test_path() to work in helper files (#1760)

And generally improve code, tests, and docs. Closes #1756. Fixes #1562.

Author: hadley

NEWS.md

@@ -1,5 +1,7 @@
 # testthat (development version)
 
+* `test_path()` now works when called within helper files (#1562).
+
 * `it()` now calls `local_test_context()` so that it behaves more
   similarly to `test_that()` (#1731), and is now exported so that you
   can more easily run BDD tests interactively (#1587)

R/test-path.R

@@ -1,23 +1,42 @@
-#' Locate file in testing directory.
+#' Locate a file in the testing directory
 #'
-#' This function is designed to work both interactively and during tests,
-#' locating files in the `tests/testthat` directory
+#' Many tests require some external file (e.g. a `.csv` if you're testing a
+#' data import function) but the working directory varies depending on the way
+#' that you're running the test (e.g. interactively, with `devtools::test()`,
+#' or with `R CMD check`). `test_path()` understands these variations and
+#' automatically generates a path relative to `tests/testthat`, regardless of
+#' where that directory might reside relative to the current working directory.
 #'
-#' @param ... Character vectors giving path component.
+#' @param ... Character vectors giving path components.
 #' @return A character vector giving the path.
 #' @export
+#' @examples
+#' \dontrun{
+#' test_path("foo.csv")
+#' test_path("data", "foo.csv")
+#' }
 test_path <- function(...) {
   if (is_testing() && !isTRUE(getOption("testthat_interactive"))) {
-    if (missing(...)) {
-      "."
-    } else {
-      file.path(...)
-    }
+    base <- NULL
+  } else if (pkgload::is_loading()) {
+    # Probably called from a helper file
+    base <- NULL
   } else {
-    base <- file.path("tests", "testthat")
+    base <- "tests/testthat"
+
     if (!dir.exists(base)) {
-      abort("Can't find `tests/testthat/` in current directory.")
+      cli::cli_abort("Can't find {.path {base}}.")
     }
-    file.path(base, ...)
+  }
+
+  file_path(base, ...)
+}
+
+file_path <- function(...) {
+  paths <- compact(list2(...))
+  if (length(paths) == 0) {
+    "."
+  } else {
+    do.call(file.path, paths)
   }
 }

man/test_path.Rd

@@ -0,0 +1,8 @@
+# throws error if can't find tests/testthat
+
+    Code
+      test_path("empty")
+    Condition
+      Error in `test_path()`:
+      ! Can't find 'tests/testthat'.
+

tests/testthat/_snaps/test-path.md

@@ -1,34 +1,45 @@
-test_that("returns local path when called in tests", {
-  expect_equal(test_path("test-test-path.R"), "test-test-path.R")
+test_that("always returns a path",{
+  withr::local_envvar(TESTTHAT = "true")
+  withr::local_options(testthat_interactive = FALSE)
 
-  # even if path doesn't (yet) exists
-  expect_equal(test_path("xxxx"), "xxxx")
+  expect_equal(test_path(), ".")
 })
 
-test_that("returns local path when called from tools::testInstalledPackages", {
-  old <- setwd("test-path-installed/testthat-tests/testthat")
-  on.exit(setwd(old))
+test_that("is vectorised", {
+  withr::local_envvar(TESTTHAT = "true")
+  withr::local_options(testthat_interactive = FALSE)
 
-  expect_equal(test_path("test-test-path.R"), "test-test-path.R")
-  expect_equal(test_path("xxxx"), "xxxx")
+  expect_equal(test_path("x", c("a", "b")), c("x/a", "x/b"))
 })
 
-test_that("returns full path when called outside tests", {
-  withr::local_dir(test_path("test-path-present"))
+test_that("uses local path when called from test_file()/tools::testInstalledPackages()", {
+  withr::local_envvar(TESTTHAT = "true")
+  withr::local_options(testthat_interactive = FALSE)
+
+  expect_equal(test_path("path"), "path")
+})
+
+test_that("returns local path during package loading", {
+  withr::local_envvar(TESTTHAT = "false", DEVTOOLS_LOAD = "testthat")
+
+  expect_equal(test_path("path"), "path")
+})
+
+test_that("returns full path when called interactively", {
   withr::local_envvar("TESTTHAT" = "false")
+  pkg <- withr::local_tempdir()
+  dir.create(file.path(pkg, "tests", "testthat"), recursive = TRUE)
+  withr::local_dir(pkg)
 
-  expect_equal(test_path("empty"), "tests/testthat/empty")
-  # even when file doesn't exist
-  expect_equal(test_path("xxx"), "tests/testthat/xxx")
+  expect_equal(test_path("path"), "tests/testthat/path")
 })
 
 test_that("throws error if can't find tests/testthat", {
-  withr::local_dir(test_path("test-path-missing"))
   withr::local_envvar("TESTTHAT" = "false")
+  withr::local_dir(withr::local_tempdir())
 
-  expect_error(test_path("empty"), "Can't find `tests/testthat/`")
-})
+  local_edition(3)
+  local_reproducible_output()
 
-test_that("test_path() always returns a path",{
-  expect_equal(test_path(), ".")
+  expect_snapshot(test_path("empty"), error = TRUE)
 })