Check e2e test code to use ExpectError()

We can use framework.ExpectError() for checking the expected error
happens. However Expect(err).To(HaveOccurred()) can be used instead
and that makes the e2e test code unreadable.
This adds the check to use framework.ExpectError() for readable code.

hack/verify-test-code.sh

@@ -20,7 +20,8 @@ set -o pipefail
 KUBE_ROOT=$(dirname "${BASH_SOURCE[0]}")/..
 cd "${KUBE_ROOT}"
 
-mapfile -t all_e2e_files < <(find test/e2e -name '*.go')
+# NOTE: This checks e2e test code without the e2e framework which contains Expect().To(HaveOccurred())
+mapfile -t all_e2e_files < <(find test/e2e -name '*.go' | grep -v 'test/e2e/framework/')
 errors_expect_no_error=()
 for file in "${all_e2e_files[@]}"
 do
@@ -30,6 +31,15 @@ do
     fi
 done
 
+errors_expect_error=()
+for file in "${all_e2e_files[@]}"
+do
+    if grep "Expect(.*)\.To(.*HaveOccurred()" "${file}" > /dev/null
+    then
+        errors_expect_error+=( "${file}" )
+    fi
+done
+
 if [ ${#errors_expect_no_error[@]} -ne 0 ]; then
   {
     echo "Errors:"
@@ -44,4 +54,18 @@ if [ ${#errors_expect_no_error[@]} -ne 0 ]; then
   exit 1
 fi
 
+if [ ${#errors_expect_error[@]} -ne 0 ]; then
+  {
+    echo "Errors:"
+    for err in "${errors_expect_error[@]}"; do
+      echo "$err"
+    done
+    echo
+    echo 'The above files need to use framework.ExpectError(err) instead of '
+    echo 'Expect(err).To(HaveOccurred()) or gomega.Expect(err).To(gomega.HaveOccurred())'
+    echo
+  } >&2
+  exit 1
+fi
+
 echo 'Congratulations!  All e2e test source files are valid.'