如何在测试中模拟外部依赖项? [英] How to mock external dependencies in tests?
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问题描述
我已经在实现中使用 extern crate 对汽车进行建模和实现:
I've modeled and implemented a car using an extern crate inside the implementation:
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?
I want to test the implementation above, but in my tests I don't want speed_control::increase()
to behave like it was in production - I want to mock it. How can I achieve this?
推荐答案
我建议你将后端函数 speed_control::increase
包装在一些 trait 中:
I would suggest you wrap the back-end function speed_control::increase
in some trait:
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() {
() => (),
}
}
}
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