MockSourceA mock is something that can be used in place of function.
('args, 'ret) t is similar to 'args -> 'ret except that:
Build an unconfigured mock. Calling an unconfigured mock will raise an exception that contains the name of the mock.
What a mock can evaluate to.
Evaluation is not possible. call will raise Mock_non_configured.
Return a value.
Raise an exception.
Define what a mock should return.
Call the mock:
call will raise this exception if the mock has not been configured.