如何为一个调用API的方法编写JUnit测试？

Question

我必须为一个调用API然后处理响应的类编写测试。类有两个公共函数和一个私有函数。第一个公共方法获取ID列表。在循环中为每个ID调用第二个公共方法，以获取与ID关联的详细信息。私有方法是在第二个公共方法内部调用的，因为获取基于id的详细信息的调用是异步进行的。

我是JUnits的新手，虽然我知道我不应该测试API调用，只是测试我的函数，但我仍然不明白单元测试应该断言什么。

public List<Integer> fetchVehicleIds(String datasetId) throws ApiException {

    VehiclesApi vehiclesApi = new VehiclesApi();

    List<Integer> vehicleIds;
    vehicleIds = vehiclesApi.vehiclesGetIds(datasetId).getVehicleIds();

    return vehicleIds;
}

 public List<VehicleResponse> fetchVehicleDetails(String datasetId, List<Integer> vehicleIds) throws InterruptedException, ApiException {

    CountDownLatch latch = new CountDownLatch(vehicleIds.size());
    List<VehicleResponse> vehiclesList = new ArrayList<>();

    for (Integer vehicleId: vehicleIds) {
        populateEachVehicleDetail(datasetId, vehicleId, vehiclesList, latch);
    }

    latch.await();

    return vehiclesList;
}

private void populateEachVehicleDetail(String datasetId, Integer vehicleId, List<VehicleResponse> vehiclesList, CountDownLatch latch) throws ApiException {

    ApiCallback<VehicleResponse> vehicleResponseApiCallback = new ApiCallback<VehicleResponse>() {
        @Override
        synchronized public void onSuccess(VehicleResponse result, int statusCode, Map<String, List<String>> responseHeaders) {
            vehiclesList.add(result);
            latch.countDown();
        }
    };

    VehiclesApi vehiclesApi = new VehiclesApi();
    vehiclesApi.vehiclesGetVehicleAsync(datasetId,vehicleId,vehicleResponseApiCallback);

}

Answer 1

这两个语句确实是您希望在单元测试中隔离的东西：

private void populateEachVehicleDetail(String datasetId, Integer vehicleId, List<VehicleResponse> vehiclesList, CountDownLatch latch) throws ApiException {
....
    VehiclesApi vehiclesApi = new VehiclesApi();
    vehiclesApi.vehiclesGetVehicleAsync(datasetId,vehicleId,vehicleResponseApiCallback);
...
}

1）让你的依赖性成为可嘲弄的

但是您只能模拟一些您可以从类的客户端设置的内容。
在这里，API是一个局部变量。因此，您应该更改类以公开依赖项，例如在构造函数中。
这样您就可以很容易地模拟它。

@Override
synchronized public void onSuccess(VehicleResponse result, int statusCode, Map<String, List<String>> responseHeaders) {
    vehiclesList.add(result);
    latch.countDown();
}

@Mock
VehiclesApi vehiclesApiMock;
// ...

// when the api method is invoked with the expected dataSetId and vehicleId
Mockito.when(vehiclesApiMock.vehiclesGetVehicleAsync(Mockito.eq(datasetId), Mockito.eq(vehicleId),
                                                 Mockito.any(ApiCallback.class)))
       // I want to invoke the callback with the mocked data
       .then(invocationOnMock -> {
           ApiCallback<VehicleResponse> callback = invocationOnMock.getArgument(2);
           callback.onSuccess(mockedVehicleResponse, mockedStatusCode,
                              mockedResponseHeaders);
           return null; // it is a void method. So no value to return in T then(...).
       });

我认为apicallback缺少一个强制转换，但您应该有总体的想法。