Mocking 数据库集<t> EF Core 5 中的 .FromSqlRaw</t>

Question

On of the repository methods happens to use FromSqlRaw to fetch the data from SQL Server via a stored procedure.

I am trying to write unit test around it but no luck so far.

This is a sample snippet of how far I got

var fixture = new Fixture();
var context = new Mock<IMyDbContext>();
var dbSet = new Mock<DbSet<MyEntity>>();
            
var data = fixture.Build<MyEntity>().CreateMany().AsQueryable();
dbSet.As<IQueryable<MyEntity>>().Setup(m => m.Provider).Returns(data.Provider);
dbSet.As<IQueryable<MyEntity>>().Setup(m => m.Expression).Returns(data.Expression);
dbSet.As<IQueryable<MyEntity>>().Setup(m => m.ElementType).Returns(data.ElementType);
dbSet.As<IQueryable<MyEntity>>().Setup(m => m.GetEnumerator()).Returns(data.GetEnumerator());
context.Setup(c => c.Set<MyEntity>()).Returns(dbSet.Object);

var repository = new MyRepository(context.Object);
 
var result = await repository.GetData();

Bit I got stuck with the following exception

System.InvalidCastException: Unable to cast object of type 'System.Linq.Expressions.ConstantExpression' to type 'Microsoft.EntityFrameworkCore.Query.QueryRootExpression'

The project uses EF Core 5.

Any idea how to solve this cast exception?

Answer 1

Don't mock IQueryable--you're just asking for a world of pain. Use a mock repository (possibly backed by an in-memory DbContext) to unit test consuming classes. Add some integration tests to verify your real repository implementation.

See Testing code that uses EF Core in the docs for more details.