如何使用 returns 数据的完成处理程序为方法编写单元测试？

Question

我一直在尝试弄清楚如何使用 OCMock 为这种方法编写单元测试。有人可以帮我吗？

- (void)executeRequest:(NSURLRequest *)request withCompletionHandler:(void (^)(id responseData, NSError *error))completionHandler
{
    NSURLSession *session = [NSURLSession sharedSession];
    NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
    if (error)
        {
            NSLog(@"Network error occurred: %@", [error localizedDescription]);
            dispatch_async(dispatch_get_main_queue(), ^(void) { completionHandler(nil, error);
            });
            return;
        }
    if ([response isKindOfClass:NSHTTPURLResponse.class])
    {
        NSInteger statusCode = [(NSHTTPURLResponse *)response statusCode];
        if (statusCode != 200)
        {
            NSLog(@"Network error occurred. Status code: %ld", (long)statusCode);
            return;
        }
    }
        completionHandler(data, nil);
    }];
    [dataTask resume];
}

Answer 1

您应该将 OCMArg 与 checkWithBlock 或 invokeBlockWithArgs 结合使用来测试完成处理程序。这里有一个例子：

点击command+N创建XCTestCase子类:

为可测试实例和必要的模拟添加属性：

@interface SomeClassTests : XCTestCase

@property (nonatomic, strong) SomeClass *testableInstance;
@property (nonatomic, strong) NSURLSession *mockSession;
@property (nonatomic, strong) NSURLRequest *mockRequest;
@property (nonatomic, strong) NSHTTPURLResponse *mockResponse;

@end

设置属性：

- (void)setUp
{
    [super setUp];
    self.testableInstance = [SomeClass new];
    self.mockSession = OCMClassMock([NSURLSession class]);
    self.mockRequest = OCMClassMock([NSURLRequest class]);
    self.mockResponse = OCMClassMock([NSHTTPURLResponse class]);
    OCMStub(ClassMethod([(id)self.mockSession sharedSession])).andReturn(self.mockSession);
}

不要忘记在拆卸时清理：

- (void)tearDown
{
    [(id)self.mockSession stopMocking];
    self.mockResponse = nil;
    self.mockRequest = nil;
    self.mockSession = nil;
    self.testableInstance = nil;
    [super tearDown];
}

我们来测试一下出现错误的情况：

- (void)testWhenErrorOccuersThenCompletionWithSameError
{
    // arrange
    NSError *givenError = [[NSError alloc] initWithDomain:@"Domain" code:0 userInfo:nil];
    OCMStub([self.mockSession dataTaskWithRequest:[OCMArg any] completionHandler:([OCMArg invokeBlockWithArgs:@"", self.mockResponse, givenError, nil])]);

    void (^givenCompletion)(id  _Nonnull, NSError * _Nonnull) = ^void(id  _Nonnull responseData, NSError * _Nonnull resultError) {
        // assert
        XCTAssertNil(responseData);
        XCTAssertEqual(resultError, givenError);
    };

    // act
    [self.testableInstance executeRequest:self.mockRequest withCompletionHandler:givenCompletion];
}

所以我们将确保如果发生某些错误，那么完成处理程序将在参数处调用相同的错误。

当我们得到一些错误的状态代码时让我们测试一下：

- (void)testWhenBadStatusCodeThenReturnWithoutCompletion
{
    // arrange
    OCMStub([self.mockResponse statusCode]).andReturn(403);
    OCMStub([self.mockSession dataTaskWithRequest:[OCMArg any] completionHandler:([OCMArg checkWithBlock:^BOOL(id param) {
        void (^passedCompletion)(NSData *data, NSURLResponse *response, NSError *error) = param;
        passedCompletion(nil, self.mockResponse, nil);
        return YES;
    }])]);

    void (^givenCompletion)(id  _Nonnull, NSError * _Nonnull) = ^void(id  _Nonnull responseData, NSError * _Nonnull resultError) {
        // assert
        XCTFail("Shouldn't be reached");
    };

    // act
    [self.testableInstance executeRequest:self.mockRequest withCompletionHandler:givenCompletion];
}

最后让我们在实际获取数据时进行测试：

- (void)testWhenSuccesThenCompletionWithSameData
{
    // arrange
    NSData *givenData = [NSData data];
    OCMStub([self.mockResponse statusCode]).andReturn(200);
    OCMStub([self.mockSession dataTaskWithRequest:[OCMArg any] completionHandler:([OCMArg checkWithBlock:^BOOL(id param) {
        void (^passedCompletion)(NSData *data, NSURLResponse *response, NSError *error) = param;
        passedCompletion(givenData, self.mockResponse, nil);
        return YES;
    }])]);

    void (^givenCompletion)(id  _Nonnull, NSError * _Nonnull) = ^void(id  _Nonnull responseData, NSError * _Nonnull resultError) {
        // assert
        XCTAssertEqual(responseData, givenData);
    };

    // act
    [self.testableInstance executeRequest:self.mockRequest withCompletionHandler:givenCompletion];
}

如果您打开覆盖范围，那么您会看到这样的测试完全覆盖了可测试代码：

如何使用 returns 数据的完成处理程序为方法编写单元测试？

How to write a unit test for a method with a completion handler that returns data?

ios

objective-c

unit-testing

nsurlsession

nsurlrequest