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// Private macros. They need to be exported and made public so they can be used // in the actual public facing macros. Ideally these would be inaccessible to // clients, but since that's not possible, we at least make it explicit that // these are intended to be private by prepending the macro names with // "__private". #[macro_export] macro_rules! __private_mock_trait_default_impl { ($mock_name:ident $(, $method:ident)*) => ( impl Default for $mock_name { fn default() -> Self { Self { $( $method: double::Mock::default() ),* } } } ); } #[macro_export] macro_rules! __private_mock_trait_new_impl { ($mock_name:ident $(, $method:ident: $retval: ty)*) => ( impl $mock_name { pub fn new( $($method: $retval),* ) -> Self { Self { $( $method: double::Mock::new($method) ),* } } } ); } /// 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: /// /// ``` /// # #[macro_use] extern crate double; /// /// mock_trait!( /// MockTaskManager, /// max_threads(()) -> u32, /// set_max_threads(u32) -> () /// ); /// /// # fn main() { /// // 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 /// /// ``` /// # #[macro_use] extern crate double; /// /// 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) -> () /// ); /// /// # fn main() { /// 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)); /// # } /// ``` #[macro_export] macro_rules! mock_trait { ($mock_name:ident $(, $method:ident($($arg_type:ty),* ) -> $retval:ty )* ) => ( #[derive(Debug, Clone)] struct $mock_name { $( $method: double::Mock<(($($arg_type),*)), $retval> ),* } __private_mock_trait_new_impl!($mock_name $(, $method: $retval)*); __private_mock_trait_default_impl!($mock_name $(, $method)*); ); (pub $mock_name:ident $(, $method:ident($($arg_type:ty),* ) -> $retval:ty )* ) => ( #[derive(Debug, Clone)] pub struct $mock_name { $( $method: double::Mock<(($($arg_type),*)), $retval> ),* } __private_mock_trait_new_impl!($mock_name $(, $method: $retval)*); __private_mock_trait_default_impl!($mock_name $(, $method)*); ); } /// Macro that generates a `struct` implementation of a trait. /// /// Use this instead of `mock_trait!` if one or more of the return types do not /// implement `Default`. If all return types implement `Default`, then it's /// more convenient to use `mock_trait!`, since you instantiate mock objects /// using `default()`, /// /// This macro generates a `struct` that implements the traits `Clone` and /// and `Debug`. Create instances of the mock object by calling `new()`, /// passing in the 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: // /// ``` /// # #[macro_use] extern crate double; /// /// // `Result` does not implement `Default`. /// mock_trait_no_default!( /// MockTaskManager, /// max_threads(()) -> Result<u32, String>, /// set_max_threads(u32) -> () /// ); /// /// # fn main() { /// // only here to make `cargo test` happy /// } /// ``` /// /// Then the following code is generated: /// /// ``` /// #[derive(Debug, Clone)] /// struct MockTaskManager { /// max_threads: double::Mock<(), Result<u32, String>>, /// set_max_threads: double::Mock<(u32), ()>, /// } /// /// impl MockTaskManager { /// pub fn new(max_threads: Result<u32, String>, set_max_threads: ()) -> Self { /// MockTaskManager { /// max_threads: double::Mock::new(max_threads), /// set_max_threads: double::Mock::new(set_max_threads), /// } /// } /// } /// ``` /// /// 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 /// /// ``` /// # #[macro_use] extern crate double; /// /// trait TaskManager { /// fn max_threads(&self) -> Result<u32, String>; /// fn set_max_threads(&mut self, max_threads: u32); /// } /// /// mock_trait_no_default!( /// MockTaskManager, /// max_threads(()) -> Result<u32, String>, /// set_max_threads(u32) -> () /// ); /// /// # fn main() { /// let mock = MockTaskManager::new(Ok(42), ()); /// assert_eq!(Ok(42), mock.max_threads.call(())); /// mock.set_max_threads.call(9001u32); /// assert!(mock.set_max_threads.called_with(9001u32)); /// # } /// ``` #[macro_export] macro_rules! mock_trait_no_default { ($mock_name:ident $(, $method:ident($($arg_type:ty),* ) -> $retval:ty )* ) => ( #[derive(Debug, Clone)] struct $mock_name { $( $method: double::Mock<(($($arg_type),*)), $retval> ),* } __private_mock_trait_new_impl!($mock_name $(, $method: $retval)*); ); (pub $mock_name:ident $(, $method:ident($($arg_type:ty),* ) -> $retval:ty )* ) => ( #[derive(Debug, Clone)] pub struct $mock_name { $( $method: double::Mock<(($($arg_type),*)), $retval> ),* } __private_mock_trait_new_impl!($mock_name $(, $method: $retval)*); ); } /// Macro that generates a mock implementation of a `trait` method. /// /// This should be used to implement a `trait` on a mock type generated by /// `double`'s `mock_trait` macro. If one has generated a mock `struct` using /// `mock_trait`, then the actual *implementation* of the desired trait can be /// auto-generated using `mock_method`, like so: /// /// ``` /// # #[macro_use] extern crate double; /// /// 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) -> () /// ); /// /// // Actually implement the trait that should be mocked /// impl TaskManager for MockTaskManager { /// mock_method!(max_threads(&self) -> u32); /// mock_method!(set_max_threads(&mut self, max_threads: u32)); /// } /// /// # fn main() { /// let mut mock = MockTaskManager::default(); /// mock.max_threads.return_value(42u32); /// assert_eq!(42, mock.max_threads()); /// assert!(mock.max_threads.called_with(())); /// mock.set_max_threads(9001u32); /// assert!(mock.set_max_threads.called_with(9001u32)); /// # } /// ``` /// /// There are many different variants of `mock_method`. In total there are 12 /// variants. 8 variants provides a combination of the following: /// /// 1. const method (`&self`) **or** mutable method (`&mut self`) /// 2. return value (`fn foo(&self) -> bool`) **or** no return value (`fn foo(&self)`) /// 3. automatically generated method body **or** custom method body /// /// (1) allows both constant and mutable methods tobe mocked, like in the /// `MockTaskManager` example above. /// /// (2) is for convenience. It means one doesn't have to specify `-> ()` /// explicitly for mocked methods that don't return values. This can also be /// shown in the `MockTaskManager` example. Notice how the return type is not /// specified when generating the `set_max_threads()` mock. /// /// (3) is useful when the stored call arguments' types (defined by the /// `mock_trait()` macro) are different to the mocked method. There are cases /// where type differences in the stored args and the actual method args are /// required. For example, suppose you had the following trait: /// /// ``` /// trait TextStreamWriter { /// fn write(text: &str); /// } /// ``` /// /// A mock can't _store_ received `text` arguments as `&str` because the mock /// needs to the _own_ the given arguments (and `&str` is a non-owning /// reference). Therefore, the mock trait has to be specified like so: /// /// ``` /// # #[macro_use] extern crate double; /// /// trait TextStreamWriter { /// fn write(&mut self, text: &str); /// } /// /// mock_trait!( /// MockTextStreamWriter, /// // have to use `String`, not `&str` here, since `&str` is a reference /// write(String) -> () /// ); /// /// impl TextStreamWriter for MockTextStreamWriter { /// mock_method!(write(&mut self, text: &str), self, { /// // manually convert the reference to an owned `String` before /// // passing it to the underlying mock object /// self.write.call(text.to_owned()) /// }); /// } /// # fn main() { /// // only here to make `cargo test` happy /// } /// ``` /// /// Using variant (3) of `mock_method` means we specify the body of the /// generated function manually. The custom body simply converts the `&str` /// argument to an owned string and passes it into the underlying `write` `Mock` /// object manually. (normally auto-generated bodies do this for you). /// /// The name of the underlying mock object is always the same as the mocked /// method's name. /// /// `&str` parameters are common. It can be inconvenient haven't to manually /// specify the body each time they appear. There are plans to add a macro to /// generate a body that calls `to_owned()` automatically. /// (TODO: implement the macro) /// /// ### Type Parameters /// /// There are an additional 4 variants to handle method type parameters /// (e.g. `fn foo<T: Eq>(&self, a: &T)`). These variants allow one to generate /// mock methods which take some generic type parameters. /// /// For example, suppose one had a `Comparator` trait that was responsible for /// comparing any two values in the program. It might look something like this: /// /// ``` /// trait Comparator { /// fn is_equal<T: Eq>(&self, a: &T, b: &T) -> bool; /// } /// ``` /// /// `T` can be multiple types. Currently, we cannot store call arguments that /// have generic types in the underlying `Mock` objects. Therefore, one has to /// convert the generic types to a different, common representation. One way /// to get around this limitation is converting each generic type to a `String`. /// e.g. for the `Comparator` trait: /// /// ``` /// # #[macro_use] extern crate double; /// /// use std::string::ToString; /// /// trait Comparator { /// fn is_equal<T: Eq + ToString>(&self, a: &T, b: &T) -> bool; /// } /// /// mock_trait!( /// MockComparator, /// // store all passed in call args as strings /// is_equal((String, String)) -> bool /// ); /// /// impl Comparator for MockComparator { /// mock_method!(is_equal<(T: Eq + ToString)>(&self, a: &T, b: &T) -> bool, self, { /// // Convert both arguments to strings and manually pass to underlying /// // mock object. /// // Notice how the both arguments as passed as a single tuple. The /// // underlying mock object always expects a single tuple. /// self.is_equal.call((a.to_string(), b.to_string())) /// }); /// } /// # fn main() { /// // only here to make `cargo test` happy /// } /// ``` /// /// If the `to_string` conversions for all `T` are not lossy, then our mock /// expectations can be exact. If the `to_string` conversions _are_ lossy, then /// this mechanism can still be used, providing all the properties of the passed /// in objects are captured in the resultant `String`s. /// /// This approach requires the writer to ensure the code under test adds the /// `ToString` trait to the `trait`'s type argument constraints. This limitation /// forces test writers to modify production code to use `double` for mocking. /// /// Despite this, there is still value in using `double` for mocking generic /// methods with type arguments. Despite adding boilerplate to production code /// and manually implementing mock method bodies being cumbersome, the value add /// is that all argument matching, expectations, calling test functions, etc. /// are all still handled by `double`. Arguably, reimplenting those features is /// more cumbersome than the small amount of boilerplate required to mock /// methods with type arguments. #[macro_export] macro_rules! mock_method { // immutable, no return value, no type parameter, no body ( $method:ident(&self $(,$arg_name:ident: $arg_type:ty)*)) => ( fn $method(&self $(,$arg_name: $arg_type)*) { self.$method.call(($($arg_name.clone()),*)) } ); // immutable, no return value, no type parameter, body ( $method:ident(&self $(,$arg_name:ident: $arg_type:ty)*), $sel:ident, $body:tt ) => ( fn $method(&$sel $(,$arg_name: $arg_type)*) $body ); // immutable, no return value, type parameter, no body // not provided, since type parameters need a custom body 99% of the time // immutable, no return value, type parameter, body ( $method:ident<($($type_params: tt)*)>(&self $(,$arg_name:ident: $arg_type:ty)*), $sel:ident, $body:tt) => ( fn $method<$($type_params)*>(&$sel $(,$arg_name: $arg_type)*) $body ); // immutable, return value, no type parameter, no body ( $method:ident(&self $(,$arg_name:ident: $arg_type:ty)*) -> $retval:ty ) => ( fn $method(&self $(,$arg_name: $arg_type)*) -> $retval { self.$method.call(($($arg_name.clone()),*)) } ); // immutable, return value, no type parameter, body ( $method:ident(&self $(,$arg_name:ident: $arg_type:ty)*) -> $retval:ty, $sel:ident, $body:tt ) => ( fn $method(&$sel $(,$arg_name: $arg_type)*) -> $retval $body ); // immutable, return value, type parameter, no body // not provided, since type parameters need a custom body 99% of the time // immutable, return value, type parameter, body ( $method:ident<($($type_params: tt)*)>(&self $(,$arg_name:ident: $arg_type:ty)*) -> $retval:ty, $sel:ident, $body:tt ) => ( fn $method<$($type_params)*>(&$sel $(,$arg_name: $arg_type)*) -> $retval $body ); // mutable, no return value, no type parameter, no body ( $method:ident(&mut self $(,$arg_name:ident: $arg_type:ty)*)) => ( fn $method(&mut self $(,$arg_name: $arg_type)*) { self.$method.call(($($arg_name.clone()),*)) } ); // mutable, no return value, no type parameter, body ( $method:ident(&mut self $(,$arg_name:ident: $arg_type:ty)*), $sel:ident, $body:tt ) => ( fn $method(&mut $sel $(,$arg_name: $arg_type)*) $body ); // mutable, no return value, type parameter, no body // not provided, since type parameters need a custom body 99% of the time // mutable, no return value, type parameter, body ( $method:ident<($($type_params: tt)*)>(&mut self $(,$arg_name:ident: $arg_type:ty)*), $sel:ident, $body:tt) => ( fn $method<$($type_params)*>(&mut $sel $(,$arg_name: $arg_type)*) $body ); // mutable, return value, no type parameter, no body ( $method:ident(&mut self $(,$arg_name:ident: $arg_type:ty)*) -> $retval:ty ) => ( fn $method(&mut self $(,$arg_name: $arg_type)*) -> $retval { self.$method.call(($($arg_name.clone()),*)) } ); // mutable, return value, no type parameter, body ( $method:ident(&mut self $(,$arg_name:ident: $arg_type:ty)*) -> $retval:ty, $sel:ident, $body:tt ) => ( fn $method(&mut $sel $(,$arg_name: $arg_type)*) -> $retval $body ); // mutable, return value, type parameter, no body // not provided, since type parameters need a custom body 99% of the time // mutable, return value, type parameter, body ( $method:ident<($($type_params: tt)*)>(&mut self $(,$arg_name:ident: $arg_type:ty)*) -> $retval:ty, $sel:ident, $body:tt ) => ( fn $method<$($type_params)*>(&mut $sel $(,$arg_name: $arg_type)*) -> $retval $body ); }