Objective C - 单元测试和测试模拟对象？

Question

- (BOOL)coolMethod:(NSString*)str
{
     //do some stuff
     Webservice *ws = [[WebService alloc] init];
     NSString *result = [ws startSynchronous:url];
     if ([result isEqual:@"Something"])
     {
         //More calculation
         return YES;
     }
     return NO;
}

我正在使用 OCUnit 在下面的方法中，我如何模拟我的 WebService 对象，或者方法“startSynchronous”的结果以便能够编写独立的单元测试？

是否可以在其中注入一些代码来创建模拟 Web 服务或在 startSynchronous 调用时返回模拟数据？

Answer 1

一种方法是使用您想要的类别和重写方法，您甚至可以重写 init 方法以返回模拟对象：

@interface Webservice (Mock)
- (id)init;
@end

@implementation Webservice (Mock)
- (id)init
{
     //WebServiceMock is a subclass of WebService
     WebServiceMock *moc = [[WebServiceMock alloc] init];
     return (Webservice*)moc;
}
@end

这样做的问题是，如果您想让对象在 1 个测试文件中的不同测试中返回不同的结果，您不能这样做。 （您可以在每个测试页面重写每个方法一次）

编辑：

这是我发布的一个老问题，我想我会更新我现在如何编写可测试代码并对其进行单元测试的答案:)

ViewController Code

@implementation MyViewController
@synthesize webService;

- (void)viewDidLoad
{
   [super viewDidLoad];

   [self.webService sendSomeMessage:@"Some_Message"];
}

- (WebService *)webService
{
   if (!_webService)
      _webService = [[WebService alloc] init];

   return _webService;
}

@end

测试代码

@implementation MyViewControllerTest

- (void)testCorrectMessageIsSentToServer
{
   MyViewController *vc = [[MyViewController alloc] init];
   vc.webService = [OCMock niceMockForClass:[WebService class]];

   [[(OCMockObject *)vc.webService expect] sendSomeMessage@"Some_Message"];
   [vc view]; /* triggers viewDidLoad */
   [[(OCMockObject *)vc.webService verify];
}

@end

Answer 2

构建在 aryaxt 的 WebService 答案之上，这里有一个小技巧，可以在不同的测试中获得不同的结果。

首先，您需要一个单例对象，用于在测试之前存储所需的答案
TestConfiguration.h

#import <Foundation/Foundation.h>
#import <objc/runtime.h>
#import <objc/message.h>


void MethodSwizzle(Class c, SEL orig, SEL new);

@interface TestConfiguration : NSObject


@property(nonatomic,strong) NSMutableDictionary *results;

+ (TestConfiguration *)sharedInstance;


-(void)setNextResult:(NSObject *)result
     forCallToObject:(NSObject *)object
              selector:(SEL)selector;


-(NSObject *)getResultForCallToObject:(NSObject *)object selector:(SEL)selector;
@end

TestConfiguration.m

#import "TestConfiguration.h"


void MethodSwizzle(Class c, SEL orig, SEL new) {
    Method origMethod = class_getInstanceMethod(c, orig);
    Method newMethod = class_getInstanceMethod(c, new);
    if(class_addMethod(c, orig, method_getImplementation(newMethod), method_getTypeEncoding(newMethod)))
        class_replaceMethod(c, new, method_getImplementation(origMethod), method_getTypeEncoding(origMethod));
    else
        method_exchangeImplementations(origMethod, newMethod);
};

@implementation TestConfiguration


- (id)init
{
    self = [super init];
    if (self) {
        self.results = [[NSMutableDictionary alloc] init];
    }
    return self;
}

+ (TestConfiguration *)sharedInstance
{
    static TestConfiguration *sharedInstance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedInstance = [[TestConfiguration alloc] init];
        // Do any other initialisation stuff here
    });
    return sharedInstance;
}


-(void)setNextResult:(NSObject *)result
     forCallToObject:(NSObject *)object
            selector:(SEL)selector
{
    NSString *className =  NSStringFromClass([object class]);
    NSString *selectorName = NSStringFromSelector(selector);

    [self.results setObject:result
                     forKey:[[className stringByAppendingString:@":"] stringByAppendingString:selectorName]];
}

-(NSObject *)getResultForCallToObject:(NSObject *)object selector:(SEL)selector
{
    NSString *className =  NSStringFromClass([object class]);
    NSString *selectorName = NSStringFromSelector(selector);

    return [self.results objectForKey:[[className stringByAppendingString:@":"] stringByAppendingString:selectorName]];

}



@end

然后，您将定义“Mock”类别来定义模拟方法，例如：

#import "MyWebService+Mock.h"
#import "TestConfiguration.h"

@implementation MyWebService (Mock)


-(void)mockFetchEntityWithId:(NSNumber *)entityId
                           success:(void (^)(Entity *entity))success
                           failure:(void (^)(NSError *error))failure
{

    Entity *response = (Entity *)[[TestConfiguration sharedInstance] getResultForCallToObject:self selector:@selector(fetchEntityWithId:success:failure:)];

    if (response == nil)
    {
        failure([NSError errorWithDomain:@"entity not found" code:1 userInfo:nil]);
    }
    else{
        success(response);
    }
}

@end

最后，在测试本身中，您将混合模拟设置中的方法，并在调用

MyServiceTest.m

- (void)setUp
{
    [super setUp];

    //swizzle webservice method call to mock object call
    MethodSwizzle([MyWebService class], @selector(fetchEntityWithId:success:failure:), @selector(mockFetchEntityWithId:success:failure:));  
}

- (void)testWSMockedEntity
{
    /* mock an entity response from the server */
    [[TestConfiguration sharedInstance] setNextResult:[Entity entityWithId:1]
                                      forCallToObject:[MyWebService sharedInstance]
                                               selector:@selector(fetchEntityWithId:success:failure:)];

    // now perform the call. You should be able to call STAssert in the blocks directly, since the success/error block should now be called completely synchronously.
}

之前定义每个测试中的预期答案备注：在我的示例中，TestConfiguration 使用类/选择器作为键而不是对象/选择器。这意味着该类的每个对象都将使用相同的选择器答案。这很可能是你的情况，因为网络服务通常是单例的。但它应该改进为对象/选择器，可能使用对象的内存地址而不是它的类