anchor.diff:  
         // THEN
         var expected = riskGameReinforcement();
  +      expected.events.addAll([//
  +        new ArmyPlaced()
  +            ..playerId = 1
  +            ..country = "eastern_australia", new NextStep()]);
  +
         expected.countries["eastern_australia"] = new CountryStateImpl(
             "eastern_australia", playerId: 1, armies: 1);
         expected.players[1].reinforcement = 0;
  
positive.code: 
        // THEN
        var expected = riskGamePlayerJoining();
        expected.started = true;
        expected.setupPhase = true;
        expected.turnStep = RiskGameState.TURN_STEP_REINFORCEMENT;
  
negative.code: 
          // THEN
          var expected = riskGameReinforcement();
          expected.events.addAll([//
            new ArmyPlaced()
                ..playerId = 1
                ..country = "eastern_australia"]);
          expected.countries["eastern_australia"] = new CountryStateImpl(
              "eastern_australia", playerId: 1, armies: 1);
          expected.players[1].reinforcement--;
  
          expectEquals(engine.game, expected);
          return expectEvents(expected.events);
        });
  
        test('should add an army on country owned by the player', () {
  