+tes #15132 Add additional overloaded expectMsg to TestKit

akka-testkit/src/main/scala/akka/testkit/TestKit.scala

@@ -332,10 +332,20 @@ trait TestKitBase {
    */
   def expectMsg[T](max: FiniteDuration, obj: T): T = expectMsg_internal(max.dilated, obj)
 
-  private def expectMsg_internal[T](max: Duration, obj: T): T = {
+  /**
+   * Receive one message from the test actor and assert that it equals the
+   * given object. Wait time is bounded by the given duration, with an
+   * AssertionFailure being thrown in case of timeout.
+   *
+   * @return the received object
+   */
+  def expectMsg[T](max: FiniteDuration, hint: String, obj: T): T = expectMsg_internal(max.dilated, obj, Some(hint))
+
+  private def expectMsg_internal[T](max: Duration, obj: T, hint: Option[String] = None): T = {
     val o = receiveOne(max)
-    assert(o ne null, s"timeout ($max) during expectMsg while waiting for $obj")
-    assert(obj == o, s"expected $obj, found $o")
+    lazy val hintOrEmptyString = hint.map(": " + _).getOrElse("")
+    assert(o ne null, s"timeout ($max) during expectMsg while waiting for $obj" + hintOrEmptyString)
+    assert(obj == o, s"expected $obj, found $o" + hintOrEmptyString)
     o.asInstanceOf[T]
   }