Macro double::mock_trait

macro_rules! mock_trait {
    ($mock_name:ident $(, $method:ident($($arg_type:ty),* ) -> $retval:ty )* ) => { ... };
    (pub $mock_name:ident $(, $method:ident($($arg_type:ty),* ) -> $retval:ty )* ) => { ... };
}

Macro that generates a struct implementation of a trait.

Use this instead of mock_trait_no_default! if all mocked method return types implement Default. If one or more of the return types do not implement Default, then mock_trait_no_default! must be used to generate the mock.

This macro generates a struct that implements the traits Clone, Debug and Default. Create instances of the mock object by calling the struct's default() method, or specify custom default return values for each mocked method using new().

The struct has a field for each method of the trait, which manages their respective method's behaviour and call expectations. For example, if one defines a mock like so:

mock_trait!(
    MockTaskManager,
    max_threads(()) -> u32,
    set_max_threads(u32) -> ()
);

    // only here to make `cargo test` happy
}

Then the following code is generated:

#[derive(Debug, Clone)]
struct MockTaskManager {
    max_threads: double::Mock<(), u32>,
    set_max_threads: double::Mock<(u32), ()>,
}

impl Default for MockTaskManager {
    fn default() -> Self {
        MockTaskManager {
            max_threads: double::Mock::default(),
            set_max_threads: double::Mock::default(),
        }
    }
}

Note that just defining this macro is not enough. This macro is used to generate the necessary boilerplate, but the generated struct does not implement the desired trait. To do that, use double's mock_method macro.

Examples

trait TaskManager {
   fn max_threads(&self) -> u32;
   fn set_max_threads(&mut self, max_threads: u32);
}

mock_trait!(
    MockTaskManager,
    max_threads(()) -> u32,
    set_max_threads(u32) -> ()
);

let mock = MockTaskManager::default();
mock.max_threads.return_value(42u32);
assert_eq!(42, mock.max_threads.call(()));
mock.set_max_threads.call(9001u32);
assert!(mock.set_max_threads.called_with(9001u32));