Objective C - 单元测试和模拟对象？

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 在以下方法中，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

一种方法是使用类别和覆盖你想要的方法，你甚至可以覆盖init方法来返回一个模拟对象：

@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，如果你想让对象在 1 个测试文件中的不同测试中返回不同的结果，你就不能这样做。 （您可以在每个测试页面覆盖每个方法一次）

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和单元测试的答案:)

ViewController 代码

@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

基于 aryaxt 的 WebService 答案，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

然后您将定义您的“模拟”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，您将在 setup 中调配模拟方法，并在调用之前在每个测试中定义预期答案

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.
}

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。这意味着类的每个对象都将为选择器使用相同的答案。这很可能是您的情况，因为 Web 服务通常是单例的。但它应该改进为一个对象/选择器，可能使用对象的内存地址而不是它的类