SPARK-884: Add unit test to validate Spark JSON output

This unit test simply validates that the outputs of
the JsonProtocol methods are syntactically valid JSON.

core/src/test/scala/org/apache/spark/deploy/JsonProtocolSuite.scala

+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ */
+
+package org.apache.spark.deploy
+
+import org.apache.spark.deploy.master.{WorkerInfo, ApplicationInfo}
+import org.scalatest.FunSuite
+import org.scalatest.matchers.ShouldMatchers
+import java.util.Date
+import net.liftweb.json.{JsonAST, JsonParser}
+import net.liftweb.json.JsonAST.JValue
+import org.apache.spark.deploy.worker.ExecutorRunner
+import org.apache.spark.deploy.DeployMessages.{WorkerStateResponse, MasterStateResponse}
+
+class JsonProtocolSuite extends FunSuite {
+  test("writeApplicationInfo") {
+    val output = JsonProtocol.writeApplicationInfo(createAppInfo())
+    assertValidJson(output)
+  }
+
+  test("writeWorkerInfo") {
+    val output = JsonProtocol.writeWorkerInfo(createWorkerInfo())
+    assertValidJson(output)
+  }
+
+  test("writeApplicationDescription") {
+    val output = JsonProtocol.writeApplicationDescription(createAppDesc())
+    assertValidJson(output)
+  }
+
+  test("writeExecutorRunner") {
+    val output = JsonProtocol.writeExecutorRunner(createExecutorRunner())
+    assertValidJson(output)
+  }
+
+  test("writeMasterState") {
+    val workers = Array[WorkerInfo](createWorkerInfo(), createWorkerInfo())
+    val activeApps = Array[ApplicationInfo](createAppInfo())
+    val completedApps = Array[ApplicationInfo]()
+    val stateResponse = new MasterStateResponse("host", 8080, workers, activeApps, completedApps)
+    val output = JsonProtocol.writeMasterState(stateResponse)
+    assertValidJson(output)
+  }
+
+  test("writeWorkerState") {
+    val executors = List[ExecutorRunner]()
+    val finishedExecutors = List[ExecutorRunner](createExecutorRunner(), createExecutorRunner())
+    val stateResponse = new WorkerStateResponse("host", 8080, "workerId", executors, finishedExecutors,
+      "masterUrl", 4, 1234, 4, 1234, "masterWebUiUrl")
+    val output = JsonProtocol.writeWorkerState(stateResponse)
+    assertValidJson(output)
+  }
+
+  def createAppDesc() : ApplicationDescription = {
+    new ApplicationDescription("name", 4, 1234, null, "sparkHome", "appUiUrl")
+  }
+  def createAppInfo() : ApplicationInfo = {
+    new ApplicationInfo(3, "id", createAppDesc(), new Date(123456789), null, "appUriStr")
+  }
+  def createWorkerInfo() : WorkerInfo = {
+    new WorkerInfo("id", "host", 8080, 4, 1234, null, 80, "publicAddress")
+  }
+  def createExecutorRunner() : ExecutorRunner = {
+    new ExecutorRunner("appId", 123, createAppDesc(), 4, 1234, null, "workerId", "host", null, null)
+  }
+
+  /* @throws ParseException if not valid json */
+  def assertValidJson(json: JValue) {
+    JsonParser.parse(JsonAST.compactRender(json))
+  }
+}