[SPARK-6980] Added UT for constructing RpcTimeout with default value

Author: BryanCutler

core/src/test/scala/org/apache/spark/rpc/RpcEnvSuite.scala

@@ -564,6 +564,13 @@ abstract class RpcEnvSuite extends SparkFunSuite with BeforeAndAfterAll {
     val rt2 = RpcTimeout(conf, Seq("spark.ask.invalid.timeout", testProp, secondaryProp), "1s")
     assert( testDurationSeconds === rt2.duration.toSeconds )
 
+    // Construct RpcTimeout with default value, 
+    val defaultProp = "spark.ask.default.timeout"
+    val defaultDurationSeconds = 1
+    val rt3 = RpcTimeout(conf, Seq(defaultProp), defaultDurationSeconds.toString + "s")
+    assert( defaultDurationSeconds === rt3.duration.toSeconds )
+    assert( rt3.message.contains(defaultProp) )
+
     // Try to construct RpcTimeout with an unconfigured property
     intercept[Throwable] {
       RpcTimeout(conf, "spark.ask.invalid.timeout")