There are two ReturnsAsync
extension methods in Moq ReturnsExtensions
class.They have following parameters:
(this IReturns<TMock, Task<TResult>> mock, TResult value)
(this IReturns<TMock, Task<TResult>> mock, Func<TResult> valueFunction)
As you can see one accepts value which should be returned by task, and another accepts delegate which will return value. When you are passing null
compiler don’t know whether it value or delegate. It’s not the case when task parameter is a value type (e.g. int). Because it cannot be null and compiler understands that null is a delegate. Probably that’s the case with your colleague’s computer.
To fix this error you need to help compiler choose correct method overload – cast null to type of task’s result (e.g. string):
RetursAsync((string)null)
Or you can pass value which is null
string s = null;
... ReturnsAsync(s);