testing: skip unrelated Cloud Run testing on PR checks (#2870)

.kokoro/build-with-run.sh

@@ -32,6 +32,59 @@ popd
 export GOOGLE_CLOUD_PROJECT=nodejs-docs-samples-tests
 pushd github/nodejs-docs-samples/${PROJECT}
 
+# Verify changes are worth testing.
+# Identify changes excluding files that have no bearing on sample functionality.
+ignore_pattern='\.md$|^\.github|\.gitignore|^LICENSE|^CODEOWNERS|^\.eslint|\.prettier|^linkinator|^renovate'
+SIGNIFICANT_CHANGES="$(git --no-pager diff --name-only main..HEAD | grep -Ev ${ignore_pattern} || true)"
+
+# If this is a PR with only insignificant changes, don't run any tests.
+if [[ -n ${KOKORO_GITHUB_PULL_REQUEST_NUMBER:-} ]] && [[ -z "$SIGNIFICANT_CHANGES" ]]; then
+  echo "No significant changes. Skipping ${PROJECT} tests."
+  exit 0
+fi
+
+# CHANGED_DIRS is the list of directories that changed.
+# CHANGED_DIRS will be empty when run on main.
+CHANGED_DIRS=$(echo "$SIGNIFICANT_CHANGES" | tr ' ' '\n' | xargs dirname 2>/dev/null || true)
+
+# Default to not running the test.
+match=0
+
+# If CHANGED_DIRS is empty, default to running the tests.
+# This ensures nightly tests will run.
+if [[ "$CHANGED_DIRS" == "" ]]; then
+  echo "Running the test: Run all tests on the main branch."
+  match=1
+fi
+
+# PROJECT is set by Kokoro to the path of the Cloud Run sample under test.
+# If any of our changed directories starts with that path, run the tests.
+# Otherwise, skip running the tests.
+# The asterisk in "$PROJECT"* is what causes the tests to run if any
+# sub-directory carries a change.
+for c in ${CHANGED_DIRS}; do
+  if [[ "$c" == "$PROJECT"* ]]; then
+    echo "Running the test: Changes found inside '{$PROJECT}'"
+    match=1
+  fi
+done
+
+# If Cloud Run related Kokoro config is changed, run the tests.
+# This matches on all Cloud Run tests if any config is modified.
+for k in '.kokoro/build-with-run.sh' '.kokoro/common.cfg' '.kokoro/.mocharc.js' '.kokoro/run'; do
+  for s in ${SIGNIFICANT_CHANGES}; do
+    if [[ "$s" == "$k"* ]]; then
+      echo "Running the test: Changes to Cloud Run .kokoro configuration detected"
+      match=1
+    fi
+  done
+done
+
+if [[ $match == 0 ]]; then
+  echo "Project ${PROJECT} had no changes."
+  exit 0
+fi
+
 # Update gcloud
 gcloud --quiet components update
 gcloud --quiet components install beta