require non-empty strings for test description

NEWS.md

@@ -1,5 +1,6 @@
 # testthat (development version)
 
+* `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).
 * `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).

R/snapshot-reporter.R

@@ -46,6 +46,7 @@ SnapshotReporter <- R6::R6Class("SnapshotReporter",
                              tolerance = testthat_tolerance(),
                              variant = NULL,
                              trace_env = NULL) {
+      check_string(self$test, allow_empty = FALSE)
       i <- self$new_snaps$append(self$test, variant, save(value))
 
       old_raw <- self$old_snaps$get(self$test, variant, i)

tests/testthat/test-snapshot.R

@@ -167,3 +167,11 @@ test_that("hint is informative", {
     cat(snapshot_accept_hint("foo", "bar.R", reset_output = FALSE))
   })
 })
+
+test_that("expect_snapshot requires a non-empty test label", {
+
+  test_that("", {
+    expect_error(expect_snapshot(1 + 1))
+  })
+
+})