I'm mocking a DbContext and its DbSets as described here.
I'd like to create a utility method for creating my mock DbContexts, which sets up each of the context's DbSets to return an empty list by default (otherwise I get errors about null references whenever I try to query one of the DbSets). Then in unit tests where I want non-empty data in a certain DbSet, I want to call Setup again on that DbSet to supply that value than I want returned. Code is below.
I did this in a unit test and it appears to be working, but I can't find anything about how Moq handles calling Setup twice on the same property. Is doing this OK, or will it have unexpected side effects? Using the debugger, I looked into context.Setups, and calling Setup a second time on the same property adds a second object to Setups rather than overwriting the first one, which worries me.
[TestClass]
public class MyTests
{
// Creates a new Mock<MyContext> and calls Setup on each property so
// that they all return empty lists
private Mock<MyContext> CreateContext()
{
Mock<MyContext> context = new Mock<MyContext>();
// CreateMockDbSet is a utility method which creates a Mock<DbSet<TEntity>>
// as described in the MSDN article listed above
context.Setup(e => e.Customers).Returns(CreateMockDbSet<Customer>().Object);
context.Setup(e => e.Orders).Returns(CreateMockDbSet<Order>().Object);
return context;
}
[TestMethod]
public void MyTest()
{
// By default, context.Customers and context.Orders will both return
// empty DbSets
Mock<MyContext> context = CreateContext();
List<Order> orders = new List<Order>
{
new Order { Id = 1 },
new Order { Id = 2 },
new Order { Id = 3 }
};
// CreateMockDbSet creates a Mock<DbSet<Order>> which returns the orders
// in 'orders'. What does Moq do when I call Setup again on 'Orders'?
context.Setup(e => e.Orders).Returns(CreateMockDbSet(orders).Object);
// ... Do test ...
}
}
https://msdn.microsoft.com/en-us/library/dn314429(v=vs.113).aspx
