Reinforce that skip is due to a package (#1959)

NEWS.md

@@ -1,5 +1,6 @@
 # testthat (development version)
 
+* `skip_if_not_installed()` produces a clearer message (@MichaelChirico, #1959).
 * `with_mock()` and `local_mock()` have been unconditionally deprecated as they will no longer work in future versions of R (#1999).
 * `expect_condition()` and friends now include the `class` of the expected condition in the failure mesage, if used (#1987).
 * `LANGUAGE` is now set to `"C"` in reprocucible environments (i.e.

R/skip.R

@@ -100,8 +100,14 @@ skip_if <- function(condition, message = NULL) {
 #' @param minimum_version Minimum required version for the package
 #' @rdname skip
 skip_if_not_installed <- function(pkg, minimum_version = NULL) {
+  # most common case: it's not installed
+  tryCatch(
+    find.package(pkg),
+    error = function(e) skip(paste0("{", pkg, "} is not installed"))
+  )
+  # rarer: it's installed, but fails to load
   if (!requireNamespace(pkg, quietly = TRUE)) {
-    skip(paste0(pkg, " cannot be loaded"))
+    skip(paste0("{", pkg, "} cannot be loaded"))
   }
 
   if (!is.null(minimum_version)) {

tests/testthat/_snaps/skip.md

@@ -26,7 +26,7 @@
 
 # skip_if_not_installed() works as expected
 
-    Reason: doesntexist cannot be loaded
+    Reason: {doesntexist} is not installed
 
 ---