feat: implement http_unit_test example (#183)

Author: coryan

examples/CMakeLists.txt

@@ -57,7 +57,8 @@ if (BUILD_TESTING)
     find_package(GTest CONFIG REQUIRED)
     set(googleapis_functions_framework_examples_unit_tests
         # cmake-format: sort
-        cloud_event_examples_test.cc http_examples_test.cc site_test.cc)
+        cloud_event_examples_test.cc http_examples_test.cc http_unit_test.cc
+        site_test.cc)
 
     foreach (fname ${googleapis_functions_framework_examples_unit_tests})
         string(REPLACE "/" "_" target "${fname}")

examples/http_unit_test.cc

@@ -0,0 +1,39 @@
+// Copyright 2020 Google LLC
+//
+// 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.
+
+// [START functions_http_unit_test]
+#include "google/cloud/functions/http_request.h"
+#include "google/cloud/functions/http_response.h"
+#include <gtest/gtest.h>
+
+namespace gcf = ::google::cloud::functions;
+extern gcf::HttpResponse hello_world_http(gcf::HttpRequest request);
+
+namespace {
+
+TEST(HttpUnitTest, Success) {
+  auto actual = hello_world_http(
+      gcf::HttpRequest{}.set_payload(R"js({ "name": "Foo" })js"));
+  EXPECT_EQ(actual.payload(), "Hello Foo!");
+
+  actual = hello_world_http(
+      gcf::HttpRequest{}.set_payload(R"js({ "unused": 7 })js"));
+  EXPECT_EQ(actual.payload(), "Hello World!");
+
+  actual = hello_world_http(gcf::HttpRequest{}.set_payload("Bar"));
+  EXPECT_EQ(actual.payload(), "Hello World!");
+}
+
+}  // namespace
+// [END functions_http_unit_test]