Moq + Unit Testing + System.Reflection.TargetParameterCountException: Parameter Count mismatch - unit-testing

Question

I am getting a "System.Reflection.TargetParameterCountException: Parameter Count mismatch" exception when attempting to mock our ApiClient.
I am using the following code to Setup the Moq response
private void SetupApiClientForGetZones(IEnumerable<Zone> zone)
{
this.MockHubApiClient.Setup(x => x.GetAsync<IEnumerable<Zone>>(It.IsAny<string>(), It.IsAny<IDictionary<string, string>>()))
.Returns(
(string name) =>
{
return zone == null ? Task.FromResult<IEnumerable<Zone>>(null) : Task.Run(() => zone);
});
this.MockApiClientFactory.Setup(x => x.CreateClient(It.IsAny<string>()))
.Returns(this.MockHubApiClient.Object);
}
The iApiClient interface I attempting to Mock is
public interface IApiClientAsync : IApiClient
{
Task<string> GetAsync(string apiController);
Task<T> GetAsync<T>(string apiController) where T : class;
Task<string> GetAsync(string apiController, IDictionary<string, string> param, string queryString);
Task<T> GetAsync<T>(string apiController, IDictionary<string, string> param) where T : class;
}
My unit test is
[Test]
public void GetZonesNotCached()
{
var data = new List<Zone> { new Zone { ZoneId = 1, ZoneName = "Test Zone 1" }, new Zone { ZoneId = 2, ZoneName = "Test Zone 2" } };
this.SetupApiClientForGetZones(data);
this.MockCache.Setup(x => x.GetItemFromCache<IEnumerable<Zone>>(It.IsAny<string>()));
var organisationService = new OrganisationService(this.MockUnitOfWorkAsync.Object, this.MockApiClientFactory.Object, this.MockCache.Object);
var results = organisationService.GetZones(1, 1).ToList();
Assert.IsNotNull(results);
Assert.AreEqual(3, results.Count, "There should be 3 records returned");
this.MockCache.Verify(x => x.GetItemFromCache<IEnumerable<Zone>>(It.IsAny<string>()), Times.Once());
this.MockHubApiClient.Verify(x => x.GetAsync<IEnumerable<Zone>>(It.IsAny<string>(), It.IsAny<IDictionary<string, string>>()), Times.Once());
}
I have found numerous other posts with the same exception but none of the solutions or examples are the same as mine.
I have been able to successfully Mock the response when calling the GetAsync method that only has the single string paramter.
private void SetupApiClientForAllDealerDetails(IEnumerable<DealerDetail> dealerDetails)
{
this.MockHubApiClient.Setup(
x => x.GetAsync<IEnumerable<DealerDetail>>(It.IsAny<string>()))
.Returns(
(string name) =>
{
return dealerDetails == null ? Task.FromResult<IEnumerable<DealerDetail>>(null) : Task.Run(() => dealerDetails);
});
this.MockApiClientFactory.Setup(x => x.CreateClient(It.IsAny<string>()))
.Returns(this.MockHubApiClient.Object);
}
Any ideas anyone?

Answer 1

If you use an expression in your .Returns instead of a value, then that expression's parameters must match those of the method signature you are mocking.
For example, I found this in SetupApiClientForGetZones:
this.MockHubApiClient.Setup(x => x.GetAsync<IEnumerable<Zone>>(It.IsAny<string>(), It.IsAny<IDictionary<string, string>>()))
.Returns(
(string name) =>
{
return zone == null ? Task.FromResult<IEnumerable<Zone>>(null) : Task.Run(() => zone);
});
When really it should be:
this.MockHubApiClient.Setup(x => x.GetAsync<IEnumerable<Zone>>(It.IsAny<string>(), It.IsAny<IDictionary<string, string>>()))
.Returns<string, IDictionary<string, string>>(
(name, dict) =>
{
return zone == null ? Task.FromResult<IEnumerable<Zone>>(null) : Task.Run(() => zone);
});