Perform xUnit Moq test to create record and save it to DbContext - unit-testing

Question

I am writing test for Web API application written in .NET CORE 3.1. I am using xUnit, AutoFixture & Moq for testing. I have a class that creates a new school instance in the database using Entity Framework/ DbContext. My question is how to mock dbContext & save changes, further my School DataModel has one: many relationships with SchoolBranch DataModel. I have followed this tutorial https://learn.microsoft.com/en-us/ef/ef6/fundamentals/testing/mocking
Error
Message:
Moq.MockException :
Expected invocation on the mock once, but was 0 times: m => m.Add<School>(It.IsAny<School>())
Performed invocations:
Mock<SchoolDbContext:1> (m):
No invocations performed.
Stack Trace:
Mock.Verify(Mock mock, LambdaExpression expression, Times times, String failMessage)
Mock`1.Verify[TResult](Expression`1 expression, Times times)
CreateSchoolCommandTest.ExecuteMethod_ShouldReturnNewGuidId_IfSuccess() line 50
School
public class School
{
public School()
{
this.SchoolBranches = new HashSet<SchoolBranch>();
}
public Guid SchoolID { get; set; }
public string Name { get; set; }
public ICollection<SchoolBranch> SchoolBranches { get; set; }
}
SchoolBranch
public class SchoolBranch
{
public SchoolBranch()
{
}
public Guid SchoolBranchID { get; set; }
public Guid SchoolID { get; set; }
public string Address { get; set; }
public int PhoneNumber { get; set; }
public School School { get; set; }
}
CreateSchool Class
public class CreateSchool : BaseCommand<Guid>, ICreateSchool
{
public SchoolDto SchoolDtos { get; set; }
public CreateSchool(IAppAmbientState appAmbient) : base(appAmbient) { }
public override Guid Execute()
{
try
{
var schoolId = Guid.NewGuid();
List<SchoolBranch> schoolBranches = new List<SchoolBranch>();
foreach(var item in SchoolDtos.SchoolBranchDtos)
{
schoolBranches.Add(new SchoolBranch()
{
SchoolBranchID = Guid.NewGuid(),
SchoolID = schoolId,
Address = item.Address,
PhoneNumber = item.PhoneNumber
});
}
var school = new School()
{
SchoolID = schoolId,
Name = SchoolDtos.Name,
SchoolBranches = schoolBranches
};
schoolDbContext.Schools.Add(school);
schoolDbContext.SaveChanges();
return school.SchoolID;
}
catch(Exception exp)
{
appAmbientState.Logger.LogError(exp);
throw;
}
}
}
Test Class
public class CreateSchoolCommandTest
{
private readonly ICreateSchool sut;
private readonly Mock<IAppAmbientState> appAmbientState = new Mock<IAppAmbientState>();
[Fact]
public void ExecuteMethod_ShouldReturnNewGuidId_IfSuccess()
{
//Arrange
var fixture = new Fixture();
var schoolDtoMock = fixture.Create<SchoolDto>();
var schoolDbSetMock = new Mock<DbSet<School>>();
var schoolBranchDbSetMock = new Mock<DbSet<SchoolBranch>>();
var schoolDbContextMock = new Mock<SchoolDbContext>();
//schoolDbSetMock.Setup(x => x.Add(It.IsAny<School>())).Returns((School s) => s); // this also did not work
schoolDbContextMock.Setup(m => m.Schools).Returns(schoolDbSetMock.Object);
//Act
sut.SchoolDtos = schoolDtoMock;
var actualDataResult = sut.Execute();
// Assert
Assert.IsType<Guid>(actualDataResult);
schoolDbContextMock.Verify(m => m.Add(It.IsAny<School>()), Times.Once());
schoolDbContextMock.Verify(m => m.SaveChanges(), Times.Once());
}
BaseCommand (DbContext is created here)
public abstract class BaseCommand<T>
{
protected SchoolDbContext schoolDbContext;
protected IAppAmbientState appAmbientState { get; }
public BaseCommand(IAppAmbientState ambientState)
{
this.schoolDbContext = new SchoolDbContext();
this.appAmbientState = ambientState;
}
public abstract T Execute();
}

Answer 1

For fix Error
You made just a little mistake. Insted of
schoolDbContextMock.Verify(m => m.Add(It.IsAny<School>()), Times.Once());
schoolDbContextMock.Verify(m => m.SaveChanges(), Times.Once());
You should have
schoolDbSetMock.Verify(m => m.Add(It.IsAny<School>()), Times.Once());
schoolDbContextMock.Verify(m => m.SaveChanges(), Times.Once());
Because you use method Add() on schoolDbContext.Schools not on schoolDbContext
For injecting dbContext
Your BaseCoommand class constructor should look like this:
public BaseCommand(IAppAmbientState ambientState, SchoolDbContext schoolDbContext)
{
this.schoolDbContext = schoolDbContext;
this.appAmbientState = ambientState;
}
Your CreateSchool class constructor:
public CreateSchool(IAppAmbientState appAmbient, SchoolDbContext schoolDbContext) : base(appAmbient, schoolDbContext) { }
And next in test you should initialize CreateSchool in test like this:
var sut = new CreateSchool(ambientState, schoolDbContextMock.Object);
And it will work