Display expected condition class (#2003)

In `expect_condition()` and friends, when `class` is supplied and the expectation fails.

Fixes #1987

Author: hadley

NEWS.md

@@ -1,5 +1,6 @@
 # testthat (development version)
 
+* `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.
   `test_that()` blocks) to disable translations. This fixes warnings
   about being unable to set the language to `"en"` (#1925).

R/expect-condition.R

@@ -278,7 +278,7 @@ expect_condition_matching <- function(base_class,
   )
 
   expected <- !identical(regexp, NA)
-  msg <- compare_condition_3e(base_class, act$cap, act$lab, expected)
+  msg <- compare_condition_3e(base_class, class, act$cap, act$lab, expected)
 
   # Access error fields with `[[` rather than `$` because the
   # `$.Throwable` from the rJava package throws with unknown fields
@@ -375,10 +375,14 @@ capture_matching_condition <- function(expr, matches) {
 
 # Helpers -----------------------------------------------------------------
 
-compare_condition_3e <- function(cond_type, cond, lab, expected) {
+compare_condition_3e <- function(cond_type, cond_class, cond, lab, expected) {
   if (expected) {
     if (is.null(cond)) {
-      sprintf("%s did not throw the expected %s.", lab, cond_type)
+      if (is.null(cond_class)) {
+        sprintf("%s did not throw the expected %s.", lab, cond_type)
+      } else {
+        sprintf("%s did not throw a %s with class <%s>.", lab, cond_type, cond_class)
+      }
     } else {
       NULL
     }

R/snapshot.R

@@ -89,7 +89,7 @@ expect_snapshot <- function(x,
   )
 
   # Use expect_error() machinery to confirm that error is as expected
-  msg <- compare_condition_3e("error", state$error, quo_label(x), error)
+  msg <- compare_condition_3e("error", NULL, state$error, quo_label(x), error)
   if (!is.null(msg)) {
     if (error) {
       expect(FALSE, msg, trace = state$error[["trace"]])
@@ -362,4 +362,3 @@ with_is_snapshotting <- function(code) {
   withr::local_envvar(TESTTHAT_IS_SNAPSHOT = "true")
   code
 }
-

tests/testthat/_snaps/expect-condition.md

@@ -25,6 +25,10 @@
     Message: dispatched!
     Class:   foobar/rlang_error/error/condition
 
+# condition class is included in failure
+
+    `f1()` did not throw a condition with class <bar>.
+
 # unused arguments generate a warning
 
     Code

tests/testthat/test-expect-condition.R

@@ -149,6 +149,11 @@ test_that("captured condition is muffled", {
   expect_error(expect_condition(stop("Hi")), NA)
 })
 
+test_that("condition class is included in failure", {
+  f1 <- function() signal(class = "foo")
+  expect_snapshot_failure(expect_condition(f1(), class = "bar"))
+})
+
 test_that("only matching condition is captured, others bubble up", {
   f1 <- function() {
     message("Hi")