You have to be careful with ReSharper, especially when it comes to invoking the test runner. It doesn't always run the compiler and, even when it does, it can use some goofy, out-of-date shadow copies. You're gonna want to double-check your syntax...
It should_return_a_concrete = _result.Data.ShouldBeOfType<IReportBase<BarChart>>;
You're missing the delegate assignment, = () =>
, and the method invocation parens at the end of the ShouldBeOfType<T>()
.