Improve failure messages for expect_visible() and expect_invisible() (#2001)

Fixes #1966

Author: hadley

NEWS.md

@@ -1,5 +1,6 @@
 # testthat (development version)
 
+* `expect_visible()` and `expect_invisible()` have improved failure messages (#1966).
 * `expect_snapshot()` now strips line breaks in test descriptions (@LDSamson, #1900).
 * `expect_snapshot()` now errors when called from a `test_that()` that has an empty description (@kevinushey, #1980).
 * `skip_if_not_installed()` produces a clearer message (@MichaelChirico, #1959).

R/expect-invisible.R

@@ -26,7 +26,7 @@ expect_invisible <- function(call, label = NULL) {
 
   expect(
     identical(vis$visible, FALSE),
-    sprintf("%s does not return invisibly", lab)
+    sprintf("%s returns visibly, not invisibly.", lab)
   )
   invisible(vis$value)
 }
@@ -39,7 +39,7 @@ expect_visible <- function(call, label = NULL) {
 
   expect(
     identical(vis$visible, TRUE),
-    sprintf("%s does not invisibly", lab)
+    sprintf("%s returns invisibly, not visibly.", lab)
   )
   invisible(vis$value)
 }

tests/testthat/_snaps/expect-invisible.md

@@ -0,0 +1,8 @@
+# generates useful failure messages
+
+    invisible(1) returns invisibly, not visibly.
+
+---
+
+    1 returns visibly, not invisibly.
+

tests/testthat/test-expect-invisible.R

@@ -6,6 +6,13 @@ test_that("basic principles of visibility hold", {
   expect_failure(expect_visible(x <- 1))
 })
 
+test_that("generates useful failure messages", {
+
+  expect_snapshot_failure(expect_visible(invisible(1)))
+  expect_snapshot_failure(expect_invisible(1))
+
+})
+
 test_that("invisibly returns evaluated value", {
   out <- expect_invisible(expect_invisible(x <- 2 + 2))
   expect_equal(out, 4)