How to unit test my models now that I am using Core Data?

core-data, objective-c, unit-testing

Solution

You need to build a Core Data stack, either within each method or in `-setUp` and then tear it down. Using an `NSInMemoryPersistentStore` will keep things fast and in-memory for your unit tests. Add a `@property (nonatomic,retain) NSManagedObjectContext *moc` to your TestCase subclass. Then:

- (void)setUp {
  NSManagedObjectModel *mom = [NSManagedObjectModel mergedModelFromBundles:[NSArray arrayWithObject:bundleContainingXCDataModel]];
  NSPersistentStoreCoordinator *psc = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:mom];
  STAssertTrue([psc addPersistentStoreWithType:NSInMemoryStoreType configuration:nil URL:nil options:nil error:NULL] ? YES : NO, @"Should be able to add in-memory store");    
  self.moc = [[NSManagedObjectContext alloc] init];
  self.moc.persistentStoreCoordinator = psc;

  [mom release];
  [psc release];

}

- (void)tearDown {
  self.moc = nil;
}

Your test method then looks like:

- (void)test_full_name_returns_correct_string {
    Patient *patient = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:self.moc];

    patient.firstName = @"charlie";
    patient.lastName = @"chaplin";
    STAssertTrue([[patient fullName] isEqualToString:@"charlie chaplin"], @"should have matched full name");
}

assuming your entity is named `Person`. There was a memory leak in your version of the method, by the way; patient should be `-release`'d in the non-Core Data version (`insertNewObjectForEntityForName:managedObjectContext:` returns an autoreleased instance).

Problem

I have been developing an iphone application using a domain model, and have put off the persistence aspect of the app until now. Core Data looks like a really good solution since I already have a well defined model but I am running into a snag with my existing unit tests. Here is simple example of what I have now: ``` - (void)test_full_name_returns_correct_string { Patient *patient = [[Patient alloc] init]; patient.firstName = @"charlie"; patient.lastName = @"chaplin"; STAssertTrue([[patient fullName] isEqualToString:@"charlie chaplin"], @"should have matched full name"); } ``` How can I make this work once my Patient object extends from NSManagedObject and uses @dynamic for the firstName and lastName properties? Has anyone else run into this type of this with Core Data? Thanks.

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