testing: add testing package to javadoc

all/build.gradle

@@ -21,6 +21,7 @@ def subprojects = [
   project(':grpc-protobuf-lite'),
   project(':grpc-protobuf-nano'),
   project(':grpc-stub'),
+  project(':grpc-testing'),
 ]
 
 for (subproject in rootProject.subprojects) {

testing/build.gradle

@@ -18,3 +18,7 @@ dependencies {
 
     testCompile project(':grpc-testing-proto')
 }
+
+javadoc {
+  exclude 'io/grpc/internal/**'
+}

testing/src/main/java/io/grpc/testing/package-info.java

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2015, gRPC Authors All rights reserved.
+ *
+ * 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.
+ */
+
+/**
+ * API that is useful for testing gRPC.
+ */
+package io.grpc.testing;