Example 1: EventAggregatorVerifyPublish

[TestMethod]
public void LoadData_SendsUpdateStatusEvents()
{
  //Arrange
  _mockEventAggregator.Setup(x => x.GetEvent<UpdateStatusEvent>().Publish(It.IsAny<string>()));
  //Act
  _materialMasterVm.LoadData().GetAwaiter();
  //Assert
  _mockEventAggregator.Verify(x => x.GetEvent<UpdateStatusEvent>().Publish(It.IsAny<string>()), Times.Exactly(2));
}

Example 2: EventAggregatorTriggerEvent

[TestMethod]
public void EventAggregator_ReceivesUpdatedUnitsEvent_CallsOnUnitsUpdated()
{
  //Arrange
  _updateUnitsEvent = new UpdatedUnitsEvent(); //Use the real event not a mock...
  //Setup the Moq EventAggregator to return our event
  _mockEventAggregator.Setup(x => x.GetEvent<UpdatedUnitsEvent>()).Returns(_updateUnitsEvent); 
   _mockUnits.Object.DensitySolid = DensitySolidSymbols.KgCm3;
   _mockUnits.Object.Pressure = PressureSymbols.KPa;
   //Act
   _updateUnitsEvent.Publish(_mockUnits.Object); //Trigger the event by publishing our payload
   //Assert
   _mockEventAggregator.Verify(x => x.GetEvent<UpdatedUnitsEvent>(), Times.Once); //Verify using Moq
   var currentItem = _materialMasterVm.MaterialModels.CurrentItem as MaterialDetailViewModel;//Check behavior
   Assert.AreEqual(DensitySolidSymbols.KgCm3, currentItem.Density.UserUnitType);
   Assert.AreEqual(PressureSymbols.KPa, currentItem.YieldStress.UserUnitType);
}