Add hack/verify-test-code.sh

This script checks coding style for test code.
It is useful to enforce developers to use framework methods for
keeping readable test code for example.

hack/verify-test-code.sh

@@ -0,0 +1,47 @@
+#!/usr/bin/env bash
+# Copyright 2019 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+KUBE_ROOT=$(dirname "${BASH_SOURCE[0]}")/..
+cd "${KUBE_ROOT}"
+
+mapfile -t all_e2e_files < <(find test/e2e -name '*.go')
+errors_expect_no_error=()
+for file in "${all_e2e_files[@]}"
+do
+    if grep "Expect(.*)\.NotTo(.*HaveOccurred()" "${file}" > /dev/null
+    then
+        errors_expect_no_error+=( "${file}" )
+    fi
+done
+
+if [ ${#errors_expect_no_error[@]} -ne 0 ]; then
+  {
+    echo "Errors:"
+    for err in "${errors_expect_no_error[@]}"; do
+      echo "$err"
+    done
+    echo
+    echo 'The above files need to use framework.ExpectNoError(err) instead of '
+    echo 'Expect(err).NotTo(HaveOccurred()) or gomega.Expect(err).NotTo(gomega.HaveOccurred())'
+    echo
+  } >&2
+  exit 1
+fi
+
+echo 'Congratulations!  All e2e test source files are valid.'