Returning different mocked values based on parameters passed in Unit Test with Moq

Question

I have a method called GetTasks() that returns 10 tasks objects. I want to moq this task for unit testing purposes. Here is the code:

 _crateRecallService.Setup(m => m.GetTasks(It.IsAny<int>(), It.IsAny<List<Stage>>(), It.IsAny<List<Severity>>())).Returns(new List<CrateRecallTaskWithComms>()
{
    new CrateRecallTaskWithComms() { CrateRecallTas = new CrateRecallTas() { CrateId = "1", PkCTaskID = 1, CampaignId = 1, Severity = "High"}},
    new CrateRecallTaskWithComms() { CrateRecallTas = new CrateRecallTas() { CrateId = "2", PkCTaskID = 2, CampaignId = 2, Severity = "High"}},
    new CrateRecallTaskWithComms() { CrateRecallTas = new CrateRecallTas() { CrateId = "3", PkCTaskID = 3, CampaignId = 3, Severity = "High"}},
    new CrateRecallTaskWithComms() { CrateRecallTas = new CrateRecallTas() { CrateId = "4", PkCTaskID = 4, CampaignId = 4}},
    new CrateRecallTaskWithComms() { CrateRecallTas = new CrateRecallTas() { CrateId = "5", PkCTaskID = 5, CampaignId = 5}},
    new CrateRecallTaskWithComms() { CrateRecallTas = new CrateRecallTas() { CrateId = "6", PkCTaskID = 6, CampaignId = 6}},
    new CrateRecallTaskWithComms() { CrateRecallTas = new CrateRecallTas() { CrateId = "7", PkCTaskID = 7, CampaignId = 7}},
    new CrateRecallTaskWithComms() { CrateRecallTas = new CrateRecallTas() { CrateId = "8", PkCTaskID = 8, CampaignId = 8}},
    new CrateRecallTaskWithComms() { CrateRecallTas = new CrateRecallTas() { CrateId = "9", PkCTaskID = 9, CampaignId = 9}},
    new CrateRecallTaskWithComms() { CrateRecallTas = new CrateRecallTas() { CrateId = "10", PkCTaskID = 10, CampaignId = 10}}

});

This works fine, but there is something missing. Filtering on Task severity would not work here.

My question is, how do I setup Moq so that if the list of Severity passed in has a High Severity within, it will return 3 instead of 10 tasks? So in other words, if I pass it:

// Arrange
var severities = new List<Severity>() { Severity.High };

I want to return 3 tasks instead of 10.

Answer 1

Returns not only accepts a value but you can also pass a delegate with an exact signature as your method and actual parameters will be passed to the delegate. Then, you can do whatever you want with these parameters. In your case

 .Returns( (int i, List<Stage> stages, List<Severity> severities) =>
          {
              if ( severities.Contains(...) 
                 return ...
              else
                 ...
          } );