Unit test controller with IConfiguration using Moq and Mock setup returns null

Question

New to Unit Testing web api. I am writing a Unit test to Test a controller and I have to mock Iconfiguration. The appsettings,json has a section called "AppSettings", I'm trying to mock it.

Also, the mock.setup returns null value in the controller causing it to fail.

Here is my controller:

    private readonly ILogger _logger;
    private readonly IConfiguration _configuration;
    private readonly ICarPairingTable PairingTable;
    private readonly ICarDealerSettingsTable DealerSettingsTable;
    static AppSettings appSettings = null;
    public CarController(IConfiguration configuration, ICarPairingTable carPairingTable, ICarDealerSettingsTable settingsTable)
    {
        _configuration = configuration;
        appSettings = configuration.Get<AppSettingsModel>().AppSettings;
        PairingTable = carPairingTable;
        DealerSettingsTable = settingsTable;
    }
    
    [HttpGet]
    public ActionResult Get(string id){
        string DealerId ="";
        
            
                DealerId = PairingTable.GetDealerId(id).Result;
                if (string.IsNullOrEmpty(DealerId))
                {
                    result = new ReturnResult
                    {
                        status = "Fail",
                        data = "ID is invalid"
                    };
                    return NotFound(result);
                }
           
           
            
            SettingsInfo info = DealerSettingsTable.GetSettingsInfo(DealerId).Result;
            if (info == null)
            {
                result = new ReturnResult
                {
                    status = "Fail",
                    data = "Not Found"
                };
                return NotFound(result);

            }
            result = new ReturnResult
            {
                status = "Success",
                data = info
            };
            return Ok(result);
    }
    

Here is my Unit Test:

   [Fact]
    public void Test1()
    {
        var mockConfig = new Mock<IConfiguration>();
        var configurationSection = new Mock<IConfigurationSection>();

        configurationSection.Setup(a => a.Value).Returns("testvalue");
        mockConfig.Setup(a => a.GetSection("AppSettings")).Returns(configurationSection.Object);

        var mock1 = new Mock<ICarPairingTable>();
       
        mock1.Setup(p => p.GetDealerId("456")).ReturnsAsync("123");
        var mock2 = new Mock<ICarDealerSettingsTable>();
        SettingsInfo mockSettings = new SettingsInfo()
        {
            DealerId = "123",
            
            Name="Dealer1"
        };
        mock2.Setup(p => p.GetSettingsInfo("123")).ReturnsAsync(()=>mockSettings);
        
        CarController controller = new CarController(mockConfig.Object,  mock1.Object, mock2.Object);
        var result = controller.Get("456");

        //Dont know what to assert

    }

Wrote unit test, but not sure if my approach is correct, Help will be appreciated.

Answer 1

This is more of a design issue wrapped in an XY problem.

Really should not be injecting IConfiguration. Based on how the configuration is using by the controller what you should have done was register the settings with the service collection in startup

Startup.ConfigureServices

//...

AppSettings appSettings = Configuration.Get<AppSettingsModel>().AppSettings;

services.AddSingleton(appSettings);

//...

and explicitly inject the settings into the controller

//...

private readonly AppSettings appSettings = null;
public CarController(AppSettings appSettings , ICarPairingTable carPairingTable, ICarDealerSettingsTable settingsTable) {
    this.appSettings = appSettings;
    PairingTable = carPairingTable;
    DealerSettingsTable = settingsTable;
}

//...

So now when unit testing the controller in isolation, you can initialize an instance of the desired class and provide when exercising the unit test.

Reference Explicit Dependencies Principle

You also appear to be mixing async-await and blocking calls like .Result.

I sugest you make the action async all the way

[HttpGet]
public async Task<ActionResult> Get(string id){
    string DealerId = await PairingTable.GetDealerId(id);
    if (string.IsNullOrEmpty(DealerId)) {
        var result = new ReturnResult {
            status = "Fail",
            data = "ID is invalid"
        };
        return NotFound(result);
    }

    SettingsInfo info = await DealerSettingsTable.GetSettingsInfo(DealerId);
    if (info == null) {
        var result = new ReturnResult {
            status = "Fail",
            data = "Not Found"
        };
        return NotFound(result);
    }
    var result = new ReturnResult {
        status = "Success",
        data = info
    };
    return Ok(result);
}

Reference Async/Await - Best Practices in Asynchronous Programming

That way the unit test can finally be arranged correctly to verify the expected behavior

[Fact]
public async Task Should_Return_Ok_ReturnRsult() {
    //Arrange
    var id = "456";
    var dealerId = "123";
    SettingsInfo expected = new SettingsInfo() {
        DealerId = dealerId,
        Name="Dealer1"
    };

    var pairingMock = new Mock<ICarPairingTable>();
    pairingMock.Setup(p => p.GetDealerId(id)).ReturnsAsync(dealerId);

    var dealerSettingsMock = new Mock<ICarDealerSettingsTable>();
    dealerSettingsMock.Setup(p => p.GetSettingsInfo(dealerId)).ReturnsAsync(() => expected);

    CarController controller = new CarController(new AppSettings(),  pairingMock.Object, dealerSettingsMock.Object);

    //Act
    var actionResult = await controller.Get(id);
    var actual = actionResult as OkObjectResult;

    //Assert (using FluentAssertions)

    actual.Should().NotBeNull();

    actual.Value.Should().BeOfType<ReturnResult>();

    var actualResult = actual.Value as ReturnResult;

    actualResult.data.Should().BeEquivalentTo(expected);        
}