title: Default context is nil when testing MagicalRecord objects with Kiwi
body: <p>I have two specs written in Kiwi, both of which call these two methods in <code>beforeAll</code>:</p>
  
  <pre><code>[MagicalRecord setDefaultModelFromClass:[self class]];
  [MagicalRecord setupCoreDataStackWithInMemoryStore];
  </code></pre>
  
  <p>And <code>[MagicalRecord cleanUp];</code> in <code>afterAll</code>.</p>
  
  <p>One of these specs fails saying <code>Default Context is nil! Did you forget to initialize the Core Data Stack?</code> but the other does not. When I comment out the first spec, the second spec still fails. When I comment out the second spec, the first spec still passes, so it doesn't seem like the order matters or they're being run in parallel and causing an issue.</p>
  
  <p>Can anyone shine some light on why this could be happening? Here is the full spec that is failing:</p>
  
  <pre><code>#import "Kiwi.h"
  #import "AuthenticationHelper.h"
  #import "Admin.h"
  
  SPEC_BEGIN(AuthenticationManagerSpec)
  
  describe(@"The authentication helper", ^{
  
      beforeAll(^{
          [MagicalRecord setDefaultModelFromClass:[self class]];
          [MagicalRecord setupCoreDataStackWithInMemoryStore];
      });
  
      afterAll(^{
          [MagicalRecord cleanUp];
      });
  
      context(@"when given correct credentials", ^{
          context(@"should pass", ^{
              NSString *email = @"foo@bar.com";
              NSString *password = @"test_password_1234";
  
              Admin *admin = [Admin createEntity];
              admin.email = email;
              admin.password = password;
  
              __block BOOL loggedInSuccessfully = NO;
              [AuthenticationHelper authenticateUserWithEmail:email
                                                        password:password
                                                      completion:^(BOOL success,
                                                                   id response) {
               loggedInSuccessfully = success;
               }];
  
              [admin deleteEntity];
  
              [[expectFutureValue(theValue(loggedInSuccessfully)) shouldEventually] beTrue];
  
          });
      });
  
  });
  
  SPEC_END
  </code></pre>
  
  <p>It fails in <code>+ (NSManagedObjectContext *) MR_defaultContext</code> with the NSAssert saying <code>Default Context is nil! Did you forget to initialize the Core Data Stack?</code>.</p>