# How to test an event-sourced command?

1. Open the respective command test suite, ex: CreateCommandTestSuite.scala

2. Grab the CommandFixture, provide

   1. provide given i.e. given these events (zero or more) have occured.
   2. provide when i.e. given this command input
   3. verify the events raised i.e. expectEventRaised

   For example:

   1. When a valid input is provided to the command, event LotteryCreated must be raised:

      test("create first lottery", Tag("create"), ptest) {
          grab[CreateCommandFixture]
            .given()
            .when(Input("TestLottery", 200))
            .expectEventRaised(EventRaised(LotteryCreated("TestLottery", 200)))
        }
      

   2. Given a lottery has already been created & ran, when you try to create another lottery - the event should be raised successfully.

     test("create another lottery", Tag("create"), ptest) {
       grab[CreateCommandFixture]
         .given(LotteryCreated(lotteryName = "FirstLottery", amount = 1000), 
           ParticipantAdded(lotteryName = "FirstLottery", participantName = "Alok", email = "alok@gmail.com"),
           ParticipantAdded(lotteryName = "FirstLottery", participantName = "Banu", email = "banu@gmail.com"),
           LotteryRan(lotteryName = "FirstLottery", winner = "Alok"))
         .when(Input("TestLottery", 200))
         .expectEventRaised(EventRaised(LotteryCreated("TestLottery", 200)))
     }
   

   2. To verify the event data use expectEventRaisedMatch

      
      
      
      
      

       

       

      
      
      

        test("lottery data match", Tag("create"), ptest) {
          grab[CreateCommandFixture]
            .given()
            .when(Input("TestLottery", 200))
            .expectEventRaisedMatch("Lottery name must be TestLottery")(e => e.created.lotteryName == "TestLottery")
            .expectEventRaisedMatch("Lottery amount must be 200")(e => e.created.amount == 200)
        }
      

   3. To print the events raised use printEventRaised

      
      
      
      
      

       

      
      
      
      

      test("lottery data match", Tag("create"), ptest) {
          grab[CreateCommandFixture]
            .given()
            .when(Input("TestLottery", 200))
            .printEventRaised
            .expectEventRaisedMatch("Lottery amount must be 200")(e => e.created.amount == 200)
        }
      

   4. To run the event handlers in order to assert the state in writeDb use runEventHandlers()

      
      
      
      
      
      

       

      
      
      
      
      
      

      test("lottery data match", Tag("create"), ptest) {
          grab[CreateCommandFixture]
            .given()
            .when(Input("TestLottery", 200))
            .expectEventRaisedMatch("Lottery amount must be 200")(e => e.created.amount == 200)
            .runEventHandlers()
          
          val lotteryExists = LotteryQuery().lotteryName.is("TestLottery").exists
          assert(lotteryExists, "Lottery has not been created")
        }
      

3. Run the testcase:

   [LotteryDomain] testOnly *CreateCommandTestSuite -- -n create
   

Note:

• Best practice is to separate the write database for test-cases using env specific configuration