我在实现中使用外部 crate 建模并实现了一辆汽车:
extern crate speed_control;
struct Car;
trait SpeedControl {
fn increase(&self) -> Result<(), ()>;
fn decrease(&self) -> Result<(), ()>;
}
impl SpeedControl for Car {
fn increase(&self) -> Result<(), ()> {
match speed_control::increase() { // Here I use the dependency
// ...
}
}
// ...
}
我想测试上面的实现,但在我的测试中我不希望 speed_control::increase()
表现得像在生产中一样 - 我想模拟它。我怎样才能做到这一点?
我建议您将后端函数 speed_control::increase
包装在某些特征中:
trait SpeedControlBackend {
fn increase();
}
struct RealSpeedControl;
impl SpeedControlBackend for RealSpeedControl {
fn increase() {
speed_control::increase();
}
}
struct MockSpeedControl;
impl SpeedControlBackend for MockSpeedControl {
fn increase() {
println!("MockSpeedControl::increase called");
}
}
trait SpeedControl {
fn other_function(&self) -> Result<(), ()>;
}
struct Car<T: SpeedControlBackend> {
sc: T,
}
impl<T: SpeedControlBackend> SpeedControl for Car<T> {
fn other_function(&self) -> Result<(), ()> {
match self.sc.increase() {
() => (),
}
}
}