Fail rspec foss-impact job with too many test files

It would recommend to add RUN AS-IF-FOSS to the merge request.

.gitlab/ci/rules.gitlab-ci.yml

@@ -422,6 +422,8 @@
   rules:
     - <<: *if-not-ee
       when: never
+    - <<: *if-merge-request-title-as-if-foss
+      when: never
     - <<: *if-security-merge-request
       changes: *code-backstage-patterns
     - <<: *if-dot-com-gitlab-org-merge-request

scripts/rspec_helpers.sh

@@ -112,9 +112,21 @@ function rspec_paralellized_job() {
 }
 
 function rspec_matched_tests() {
+  local test_file_count_threshold=20
   local matching_tests_file=${1}
   local rspec_opts=${2}
   local test_files="$(cat "${matching_tests_file}")"
+  local test_file_count=$(wc -w "${matching_tests_file}" | awk {'print $1'})
+
+  if [[ "${test_file_count}" -gt "${test_file_count_threshold}" ]]; then
+    echo "There are more than ${test_file_count_threshold} FOSS test files matched,"
+    echo "which would take too long to run in this job."
+    echo "To reduce the likelihood of breaking FOSS pipelines,"
+    echo "please add [RUN AS-IF-FOSS] to the MR title and restart the pipeline."
+    echo "This would run all as-if-foss jobs in this merge request"
+    echo "and remove this job from the pipeline."
+    exit 1
+  fi
 
   if [[ -n $test_files ]]; then
     rspec_simple_job "${rspec_opts} ${test_files}"