OCMock expect a class method

Question

So I want to be able to expect a class method being called for one of my classes

@implementation CustomClass

+ (void)method:(NSString*)string{
    [[self class] method:string object:nil];

}

+ (void)method:(NSString *)string object:(id)object {
    //do something with string and object
}

@end

and I want to call [CustomClass method:@""] and expect method: string:

I've tried method swizzling but it seems like that is only useful for stubbing.

Answer 1

You can test that both using method swizzling or OCMock.

With method swizzling, first of all we declare the following variables in your test implementation file:

static NSString *passedString;
static id passedObject;

Then we implement a stub method(in the test class) and go with the swizzling:

+ (void)stub_method:(NSString *)string object:(id)object
{
    passedString = string;
    passedObject = object;
}

- (void) test__with_method_swizzling
{
    // Test preparation 
    passedString = nil;
    passedObject = [NSNull null];// Whatever object to verify that we pass nil

    Method originalMethod =
        class_getClassMethod([CustomClass class], @selector(method:object:));
    Method stubMethod =
        class_getClassMethod([self class], @selector(stub_method:object:));

    method_exchangeImplementations(originalMethod, stubMethod);

    NSString * const kFakeString = @"fake string";

    // Method to test
    [CustomClass method:kFakeString];

    // Verifications
    STAssertEquals(passedString, kFakeString, nil);
    STAssertNil(passedObject, nil);

    method_exchangeImplementations(stubMethod, originalMethod);
}

But we can accomplish the same with OCMock in a much simpler way:

- (void) test__with_OCMock
{
    // Test preparation 
    id mock = [OCMockObject mockForClass:[CustomClass class]];

    NSString * const kFakeString = @"fake string";
    [[mock expect] method:kFakeString object:nil];

    // Method to test
    [CustomClass method:kFakeString];

    // Verifications 
    [mock verify];
}