Unit Testing Entity Framework 6 DbContext

The Entity Framework version 6 has good unit testing possibilities and the documentation provided by MSDN provides a good starting point...

The main thing to remember is that you need to create a TestDbSet for each context property that is going to be used:

	ITimesheetsContext _context = MockRepository.GenerateStub<ITimesheetsContext>();
	_context.Departments = new TestDbSet<Department>();
	_context.Timesheets = new TestDbSet<Timesheet>();
	_context.Employees = new TestDbSet<Employee>();
	_context.Stub(c => c.SaveChangesAsync()).Return(Task.FromResult(0));

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Then you can add data to your Entities as per usual when setting up the in memory datastore:

	context.Departments.Add(new Department() { Id = 1, Name = "Department 1" });
	context.Departments.Add(new Department() { Id = 2, Name = "Department 2" });
	context.Employees.Add(new Employee() { Id = 1, ForeName = "John" });
	context.Employees.Add(new Employee() { Id = 2, ForeName = "Mark" });
	context.Employees.Add(new Employee() { Id = 3, ForeName = "Mat" });

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The MSDN documentation provides a TestDbSet class which provides a fake collection for the context properties (reproduced here for completeness):

	public class TestDbSet<TEntity> : DbSet<TEntity>, IQueryable, IEnumerable<TEntity>, IDbAsyncEnumerable<TEntity>
	where TEntity : class
	{
	ObservableCollection<TEntity> _data;
	IQueryable _query;

	public TestDbSet()
	{
	_data = new ObservableCollection<TEntity>();
	_query = _data.AsQueryable();
	}

	public override TEntity Add(TEntity item)
	{
	_data.Add(item);
	return item;
	}

	public override TEntity Remove(TEntity item)
	{
	_data.Remove(item);
	return item;
	}

	public override TEntity Attach(TEntity item)
	{
	_data.Add(item);
	return item;
	}

	public override TEntity Create()
	{
	return Activator.CreateInstance<TEntity>();
	}

	public override TDerivedEntity Create<TDerivedEntity>()
	{
	return Activator.CreateInstance<TDerivedEntity>();
	}

	public override ObservableCollection<TEntity> Local
	{
	get { return _data; }
	}

	Type IQueryable.ElementType
	{
	get { return _query.ElementType; }
	}

	Expression IQueryable.Expression
	{
	get { return _query.Expression; }
	}

	IQueryProvider IQueryable.Provider
	{
	get { return new TestDbAsyncQueryProvider<TEntity>(_query.Provider); }
	}

	System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
	{
	return _data.GetEnumerator();
	}

	IEnumerator<TEntity> IEnumerable<TEntity>.GetEnumerator()
	{
	return _data.GetEnumerator();
	}

	IDbAsyncEnumerator<TEntity> IDbAsyncEnumerable<TEntity>.GetAsyncEnumerator()
	{
	return new TestDbAsyncEnumerator<TEntity>(_data.GetEnumerator());
	}
	}

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