ios - MagicalRecord MR_createInContext : returns nil

Question

我有以下方法:

+(Group*)groupWithID:(NSString *)idNumber
           inContext:(NSManagedObjectContext *)context
{
    Group *group = nil;
    if(idNumber && context)
    {
        NSArray *result = [Group MR_findByAttribute:@"idNumber" withValue:idNumber inContext:context];
        if(!result || result.count > 1)
        {
            // TODO (Robert): Handle error for more than one group objects or error nil results
        }
        else if(result.count == 0)
        {
            group = [Group MR_createInContext:context];
            group.idNumber = idNumber;
            NSAssert(group != nil, @"Group should not be nil!");
        }
        else
        {
            group = [result lastObject];
        }
    }

    return group;
}

我正在使用以下 Kiwi 规范对其进行测试:

it(@"should create new object with new id", ^{
    [[[Group class] should] receive:@selector(MR_createInContext:)];
    Group *group = [Group groupWithID:@"12345"
                            inContext:[NSManagedObjectContext MR_contextForCurrentThread]];
    [[group should] beNonNil];
    [[[group idNumber] should] equal:@"12345"];
});

使用以下设置:

beforeEach(^{
        [MagicalRecord setupCoreDataStackWithInMemoryStore];
        [MagicalRecord setDefaultModelNamed:@"Model.mom"];
    });

    afterEach(^{
        [MagicalRecord cleanUp];
    });

问题是方法 MR_createInContext 返回一个 nil，我不知道可能是什么原因，因为在其他一些测试中，相同的代码会产生一个有效的非 nil 对象。

Answer 1

正如您所发现的，当您设置 receive期望，Kiwi 在对象上 stub 该方法，无论它是否是常规对象，Class对象，或实际的 Kiwi 模拟/测试替身 (https://github.com/allending/Kiwi/wiki/Expectations#expectations-interactions-and-messages)。

如果您要测试的是您的 +groupWithID:inContext:助手行为正确，您实际上并不想要 MR_createInContext: 的真正实现. “应该收到”的期望旨在测试您是否发送了正确的消息，但要避免执行实际代码。

也许是这样的:

it(@"creates a new group if one does not exist with the specified id", ^{
    // stub MR_findByAttribute to return no results
    [Group stub:@selector(MR_findByAttribute:withValue:inContext:) andReturn:@[]];

    // stub MR_createInContext to use our test group so that we can set
    // expectations on it
    id context = [NSManagedObject MR_defaultContext];
    id group = [Group MR_createInContext:context];
    [[Group should] receive:@selector(MR_createInContext:) andReturn:group withArguments:context];

    // call the method we want to test
    [Group groupWithID:@"1234" inContext:context];

    // test that the id was set correctly
    [[group.idNumber should] equal:@"1234"];
});