Unable to mock NSUserDefaults - ios

Question

I don't seem to be able to mock NSUserDefaults. I want it to send back the data that I tell it too but instead, it sends back the data stored in it from when running the app.
I am using:
Specta
Expecta
OCMockito
I have the following test:
describe(#"AppDelegate", ^{
__block AppDelegate *appDelegate;
beforeEach(^{
appDelegate = [AppDelegate new];
});
afterEach(^{
appDelegate = nil;
});
describe(#"application did finish launching with options", ^{
beforeEach(^{
[appDelegate application:nil didFinishLaunchingWithOptions:nil];
NSUserDefaults *mockUserDefaults = mock([NSUserDefaults class]);
[given([mockUserDefaults objectForKey:#"currentUser"]) willReturn:nil];
});
it(#"should have a login view controller as root view controller", ^{
expect(appDelegate.window.rootViewController).to.beKindOf([ToALoginViewController class]);
});
});
});
So the above test fails because it actually returns some data for currentUser. What am I doing wrong?
Following on from what Ken Kuan said, I made the following changes:
AppDelegate.h
#property (strong, nonatomic) NSUserDefaults *userDefaults;
- (void)setUserDefaults:(NSUserDefaults *)userDefaults;
AppDelegate.m
- (void)setUserDefaults:(NSUserDefaults *)userDefaults {
_userDefaults = userDefaults;
}
AppDelegateSpec.m
beforeEach(^{
[appDelegate application:nil didFinishLaunchingWithOptions:nil];
NSUserDefaults *mockUserDefaults = mock([NSUserDefaults class]);
[appDelegate setUserDefaults:mockUserDefaults];
[given([mockUserDefaults objectForKey:#"currentUser"]) willReturn:nil];
});
However, I still get the same problem.

Answer 1

You can mock NSUserDefaults. I have this code which is working fine.
When you are mocking NSUserdefaults make sure you are stopping mock at the end of test case, otherwise it would cause errors in other places where you are using NSUserDefaults.
id userDefaultsMock = OCMClassMock([NSUserDefaults class]);
OCMStub([userDefaultsMock standardUserDefaults]).andReturn(userDefaultsMock);
OCMStub([[userDefaultsMock standardUserDefaults] boolForKey:SHOWMYNAME]).andReturn(#"N");
[self.myObject codewithuserdefaults];
OCMVerify( [[NSUserDefaults standardUserDefaults] setValue:[OCMArg any] forKey:FIRSTNAME]);
[userDefaultsMock stopMocking];

Answer 2

You must use [NSUserDefaults standardUserDefaults] in appDelegate which is actual user defaults, not your mock.
A solution is to make user default to a property of app delegate and set it with your mockUserDefaults in tests.
Another one is to swizzle [NSUserDefaults standardUserDefaults] to return your mockUserDefaults in your tests.

Answer 3

So with much thanks to Ken Kuan, I managed to solve the problem I was having. Heres how I achieved it.
I added a NSUserDefaults property to the AppDelegate and a setter function.
I set self.userDefaults to [NSUserDefaults standardUserDefaults] in application:willFinishLaunchingWithOptions:.
I then set the rootViewController in application:didFinishLaunchingWithOptions:
AppDelegate.h
#property (strong, nonatomic) NSUserDefaults *userDefaults;
- (void)setUserDefaults:(NSUserDefaults *)userDefaults;
AppDelegate.m
- (BOOL)application:(UIApplication *)application willFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.userDefaults = [NSUserDefaults standardUserDefaults];
return YES;
}
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
NSData *encodedUserData = [self.userDefaults objectForKey:#"currentUser"];
if (encodedUserData) {
NSLog(#"Have current user");
self.window.rootViewController = [ThermostatViewController new];
} else {
NSLog(#"No current user");
self.window.rootViewController = [ToALoginViewController new];
}
[self.window makeKeyAndVisible];
return YES;
}
- (void)setUserDefaults:(NSUserDefaults *)userDefaults {
_userDefaults = userDefaults;
}
AppDelegateSpec.m
describe(#"application will finish launching with options", ^{
beforeEach(^{
[appDelegate application:nil willFinishLaunchingWithOptions:nil];
});
context(#"application did finish launching with options and with no current user", ^{
beforeEach(^{
NSUserDefaults *mockUserDefaults = mock([NSUserDefaults class]);
[appDelegate setUserDefaults:mockUserDefaults];
[given([mockUserDefaults objectForKey:#"currentUser"]) willReturn:nil];
[appDelegate application:nil didFinishLaunchingWithOptions:nil];
});
it(#"should have a login view controller as root view controller", ^{
expect(appDelegate.window.rootViewController).to.beKindOf([ToALoginViewController class]);
});
});
});