protected override async Task Context()
        {
            await base.Context();

            _snapshot = await sut.MapToSnapshot(_tableFormula);

            _snapshot.UseDerivedValues = false;
            A.CallTo(_formulaFactory).WithReturnType <TableFormula>().Returns(new TableFormula {
                UseDerivedValues = true
            });
        }
 protected override async Task Because()
 {
     _snapshot = await sut.MapToSnapshot(_tableFormula);
 }