Improve Unit Test with OCMock

Adding OCMock to your project:

• Step 1: Download a release from the downloads page.
• Step 2: Setup OCMock from the iOS page.
• Step 3: Add an import to your unit tests.

#import <OCMock/OCMock.h>

Contents:

1. Example classes
2. Expect-run-verify
3. Verify-after-running
4. Void-Method
5. Return-Method
6. Block
7. Delegate and DataSource
8. Notification (Observer)
9. Exception
10. Advanced topics

• 1. Example classes

Let's assume we are writing a little application. Our application have two classes as ClassA and ClassB. ClassB inherit from ClassA. They have some methods as below:

	#import <Foundation/Foundation.h>
	static NSString* const NOTIFICATION_OF_CLASS = @"NotificationOfClass";
	@class ClassA;
	@class ClassB;
	@protocol ClassADelegate <NSObject>
	- (void)responsedValue:(ClassA*)class value:(NSString*)aValue;
	@end
	@interface ClassA : NSObject {
	@public
	ClassB* publicClass;
	}
	@property (nonatomic, assign) id delegate;
	- (void)executeVoidMethod;
	- (void)executeVoidMethodAndSubVoidMethod;
	- (void)executeVoidMethodAndReturnMethod;
	- (void)executeBlockMethod:(void(^)(NSString* returnedValue))aBlock;
	- (NSString*)executeReturnMethodAndSubBlock;
	- (void)executeVoidMethodAndDelegate;
	- (void)executeVoidMethodAndNotification;
	- (void)executeVoidMethodAndException:(NSString*)aParam;
	- (void)executeRejectMethod;
	@end

view raw ClassA_h hosted with ❤ by GitHub

	#import "ClassA.h"
	#import "ClassB.h"
	@implementation ClassA
	- (void)executeVoidMethod {
	NSLog(@"Void_%@",[self class]);
	}
	- (void)executeVoidMethodAndSubVoidMethod {
	if (publicClass) {
	//Comment this code and run "testSubVoidMethod_UsingClassMock"
	[publicClass executeVoidMethod];
	//End
	}
	}
	- (void)executeVoidMethodAndReturnMethod {
	if (publicClass) {
	//You can comment these codes and run "testStubActionsAndExpect_UsingClassMock"
	NSString* value = [publicClass executeReturnMethod];
	NSLog(@"%@",value);
	//End
	}
	}
	- (void)executeBlockMethod:(void(^)(NSString* returnedValue))aBlock {
	aBlock([NSString stringWithFormat:@"Block_%@",[self class]]);
	}
	- (NSString*)executeReturnMethodAndSubBlock {
	__block NSString* value = @"DefaultValue";
	if (publicClass) {
	[publicClass executeBlockMethod:^(NSString *returnedValue) {
	value = returnedValue;
	}];
	}
	return value;
	}
	- (void)simulateDelegate {
	if ([_delegate respondsToSelector:@selector(responsedValue:value:)]) {
	[_delegate responsedValue:self value:@"DelegateValue"];
	}
	}
	- (void)executeVoidMethodAndDelegate {
	[self performSelector:@selector(simulateDelegate)
	withObject:nil afterDelay:2];
	}
	- (void)executeVoidMethodAndNotification {
	[[NSNotificationCenter defaultCenter] postNotificationName:NOTIFICATION_OF_CLASSA
	object:nil];
	}
	- (void)simulateException:(NSString*)aParam {
	if (!aParam) {
	[[NSException exceptionWithName:@"ABC" reason:@"Non" userInfo:nil] raise];
	}
	NSLog(@"Run fine");
	}
	- (void)executeVoidMethodAndException:(NSString*)aParam {
	@try {
	if (!publicClass) {
	[[NSException exceptionWithName:@"Object" reason:@"Non" userInfo:nil] raise];
	}
	[publicClass simulateException:aParam];
	}
	@catch (NSException *exception) {
	NSLog(@"%@",exception);
	}
	@finally {
	NSLog(@"Final");
	}
	}
	- (void)executeRejectMethod {
	if (publicClass) {
	//Uncomment this code and run "testRejectActions_UsingClassMock"
	// [publicClass executeReturnMethod];
	}
	}
	@end

view raw ClassA_m hosted with ❤ by GitHub

	#import <Foundation/Foundation.h>
	#import "ClassA.h"
	@interface ClassB : ClassA
	- (NSString*)executeReturnMethod;
	- (void)executeMethodWithOrder1;
	- (void)executeMethodWithOrder2;
	@end

view raw ClassB_h hosted with ❤ by GitHub

	#import "ClassB.h"
	@implementation ClassB
	- (NSString*)executeReturnMethod {
	return @"ClassB";
	}
	- (void)executeMethodWithOrder1 {
	NSLog(@"First");
	}
	- (void)executeMethodWithOrder2 {
	NSLog(@"Second");
	}
	- (void)executeRejectMethod {
	//Uncomment this code and run "testRejectActions_UsingPartialMock"
	// [self executeReturnMethod];
	//End
	}
	@end

view raw ClassB_m hosted with ❤ by GitHub

• 2. Expect-run-verify

This is the original approach to mocking. First the mock object is set up with expectations, then the code under test is run, and afterwards the expectations are verified. If an expected method has not been invoked, or has not been invoked with the right arguments, then an error is reported. As shown it is possible to use argument constraints in the expect statement. Strict mocks can be created for classes and protocols.
Example codes:

	//Definition of the category Test on the classA
	@interface ClassA (PrivateMethodTest)
	- (void)simulateException:(NSString*)aParam;
	@end
	- (void)testExpectRunVerify_UsingClassMock {
	//GIVEN
	ClassA* object = [[ClassA alloc] init];
	id classMock = OCMClassMock([ClassB class]);
	OCMExpect([classMock simulateException:@"@congpc.ios"]);
	object->publicClass = classMock;
	//WHEN /* run code under test */
	[object executeVoidMethodAndException:@"@congpc.ios"];
	//THEN
	OCMVerifyAll(classMock);
	}
	- (void)testExpectRunVerify_UsingStrictMock {
	//GIVEN
	ClassA* object = [[ClassA alloc] init];
	id strictMock = OCMStrictClassMock([ClassB class]);
	OCMExpect([strictMock simulateException:@"@congpc.ios"]);
	object->publicClass = strictMock;
	//WHEN /* run code under test */
	[object executeVoidMethodAndException:@"@congpc.ios"];
	//THEN
	OCMVerifyAll(strictMock);
	}

view raw ExpectRunVerify hosted with ❤ by GitHub

• 3. Verify after running

Verifies that some method has been called by the code under test. If the method has not been invoked an error is reported. In Xcode and AppCode the error is reported on the line of the verify, for other test environments an exception is thrown.
Base on the example of "Expect-Run-Verify", I rewrite as below:

	- (void)testVerifyAfterRunning_UsingClassMock {
	//GIVEN
	ClassA* object = [[ClassA alloc] init];
	id classMock = OCMClassMock([ClassB class]);
	object->publicClass = classMock;
	//WHEN /* run code under test */
	[object executeVoidMethodAndException:@"@congpc.ios"];
	//THEN
	OCMVerify([classMock simulateException:@"@congpc.ios"]);
	}
	- (void)testVerifyAfterRunning_UsingStrictMock {
	//GIVEN
	ClassA* object = [[ClassA alloc] init];
	id classMock = OCMStrictClassMock([ClassB class]);
	object->publicClass = classMock;
	//WHEN /* run code under test */
	[object executeVoidMethodAndException:@"@congpc.ios"];
	//THEN
	OCMVerify([classMock simulateException:@"@congpc.ios"]);
	}

view raw VerifyAfterRunning hosted with ❤ by GitHub

• 4. Void-Method

You can use ClassMock, PartialMock for test void method.

	#pragma mark - Using OCMock for void method
	- (void)testVoidMethod_UsingClassMock {
	//GIVEN
	id objectMock = OCMClassMock([ClassA class]);
	//WHEN /* run code under test */
	[objectMock executeVoidMethod];
	//THEN
	OCMVerify([objectMock executeVoidMethod]);
	}
	- (void)testVoidMethod_UsingClassMockAndExpect {
	//GIVEN
	id objectMock = OCMClassMock([ClassA class]);
	[[objectMock expect] executeVoidMethod];
	//WHEN /* run code under test */
	[objectMock executeVoidMethod];
	//THEN
	OCMVerifyAll(objectMock);
	}
	- (void)testVoidMethod_UsingPatialMock {
	//GIVEN
	ClassA* object = [[ClassA alloc] init];
	id objectMock = OCMPartialMock(object);
	//WHEN /* run code under test */
	[object executeVoidMethod];
	//THEN
	OCMVerify([objectMock executeVoidMethod]);
	}
	- (void)testVoidMethod_UsingPatialMockAndExpect {
	//GIVEN
	ClassA* object = [[ClassA alloc] init];
	id objectMock = OCMPartialMock(object);
	[[objectMock expect] executeVoidMethod];
	//WHEN /* run code under test */
	[object executeVoidMethod];
	//THEN
	OCMVerifyAll(objectMock);
	}
	#pragma mark Sub void method
	- (void)testSubVoidMethod_UsingClassMock {
	//GIVEN
	ClassA* object = [[ClassA alloc] init];
	id objectMock = OCMClassMock([ClassB class]);
	object->publicClass = objectMock;
	//WHEN /* run code under test */
	[object executeVoidMethodAndSubVoidMethod];
	//THEN
	OCMVerify([objectMock executeVoidMethod]);
	}
	- (void)testSubVoidMethod_UsingClassMockAndExpect {
	//GIVEN
	ClassA* object = [[ClassA alloc] init];
	id objectMock = OCMClassMock([ClassB class]);
	[[objectMock expect] executeVoidMethod];
	object->publicClass = objectMock;
	//WHEN /* run code under test */
	[object executeVoidMethodAndSubVoidMethod];
	//THEN
	OCMVerifyAll(objectMock);
	}

view raw VoidMethod hosted with ❤ by GitHub

• 5. Return-Method

You can use ClassMock, PartialMock for simulate the value is returned.

	- (void)testReturnMethod_UsingClassMockAndStub {
	//GIVEN
	NSString* inputedValue = @"Simulated value";
	id objectMock = OCMClassMock([ClassB class]);
	OCMStub([objectMock executeReturnMethod]).andReturn(inputedValue);
	//WHEN /* run code under test */
	NSString* returnedValue = [objectMock executeReturnMethod];
	//THEN
	XCTAssertEqualObjects(inputedValue, returnedValue);
	}
	- (void)testReturnMethod_UsingPartialMockAndStub {
	//GIVEN
	NSString* inputedValue = @"Simulated value";
	ClassB* object = [[ClassB alloc] init];
	//You can comment these codes and run again.
	id objectMock = OCMPartialMock(object); //Real object
	OCMStub([objectMock executeReturnMethod]).andReturn(inputedValue);
	//End comment
	//WHEN /* run code under test */
	NSString* returnedValue = [object executeReturnMethod];
	//THEN
	XCTAssertEqualObjects(inputedValue, returnedValue);
	}

view raw ReturnMethod hosted with ❤ by GitHub

• 6. Block

You can use ClassMock, PartialMock, andDo for simulate the value is returned from a block.

	- (void)testBlockMethod_UsingClassMock {
	//GIVEN
	NSString* expectedValue = @"@congpc.ios";
	ClassA* object = [[ClassA alloc] init];
	//Simulate returned value of a block. You can comment these codes and run again.
	id objectMock = OCMClassMock([ClassB class]);
	[[[objectMock stub] andDo:^(NSInvocation *invocation) {
	void (^successBlock)(NSString* value);
	//Remember that self and _cmd are arguments 0 and 1.
	[invocation getArgument:&successBlock atIndex:2];
	successBlock(@"@congpc.ios");
	}] executeBlockMethod:OCMOCK_ANY];
	object->publicClass = objectMock;
	//End comment
	//WHEN /* run code under test */
	NSString* returnedValue = [object executeReturnMethodAndSubBlock];
	//THEN
	XCTAssertEqualObjects(expectedValue, returnedValue);
	}

view raw Block hosted with ❤ by GitHub

• 7. Delegate and DataSource

You can use ProtocolMock for simulate a delegate or a datasource.

	- (void)testDelegate_UsingClassMockAndExpect_VerifyWithDelay {
	//GIVEN
	ClassA* object = [[ClassA alloc] init];
	id delegateMock = OCMProtocolMock(@protocol(ClassADelegate));
	// set an expectation
	[[delegateMock expect] responsedValue:object value:@"DelegateValue"];
	object.delegate = delegateMock;
	//WHEN
	[object executeVoidMethodAndDelegate];
	//THEN
	OCMVerifyAllWithDelay(delegateMock, 2);
	}

view raw Delegate hosted with ❤ by GitHub

Simulate the datasource of TableView

	- (void)testDataSourceOfTableView {
	// create the code under test
	UITableView *tableView = [[UITableView alloc] init];
	// create a protocol mock
	id mockDataSource = OCMProtocolMock(@protocol(UITableViewDataSource));
	// stub a protocol query
	[OCMStub([mockDataSource numberOfSectionsInTableView:tableView]) andReturnValue:[NSNumber numberWithInteger:4]];
	// give the mock to the code under test
	[tableView setDataSource:mockDataSource];
	// execute the code under test
	NSInteger n = [tableView numberOfSections];
	// verify results
	XCTAssertEqual(4, n, @"should have 4 sections");
	}

view raw DataSource hosted with ❤ by GitHub

• 8. Notification (Observer)

You can use ObserverMock for test NotificationCenter.

	- (void)testNotification_UsingObserverMockAndExpect {
	//GIVEN
	ClassA* object = [[ClassA alloc] init];
	id observerMock = OCMObserverMock();
	// set an expectation
	OCMExpect([observerMock notificationWithName:NOTIFICATION_OF_CLASS
	object:nil]);
	// register the mock observer with an NSNotificationCenter
	[[NSNotificationCenter defaultCenter] addMockObserver:observerMock
	name:NOTIFICATION_OF_CLASS
	object:nil];
	//WHEN
	[object executeVoidMethodAndNotification];
	//THEN
	OCMVerifyAll(observerMock);
	}
	- (void)testNotification_UsingClassMockAndObserverMockAndStubAndPost {
	//GIVEN
	id observerMock = OCMObserverMock();
	NSNotification* aNotification = [observerMock notificationWithName:NOTIFICATION_OF_CLASS
	object:nil];
	ClassA* object = [[ClassA alloc] init];
	id classMock = OCMClassMock([ClassB class]);
	OCMStub([classMock executeVoidMethod]).andPost(aNotification);
	object->publicClass = classMock;
	// register the mock observer with an NSNotificationCenter
	[[NSNotificationCenter defaultCenter] addMockObserver:observerMock
	name:NOTIFICATION_OF_CLASS
	object:nil];
	//WHEN
	[object executeVoidMethodAndSubVoidMethod];
	//THEN
	OCMVerifyAll(classMock);
	OCMVerifyAll(observerMock);
	}

view raw NotificationCenter hosted with ❤ by GitHub

• 9. Exception

You can use StrictClassMock for test Exception.

	- (void)testException_UsingStrictMock_FailingFast {
	//GIVEN
	id strictMock = OCMStrictClassMock([ClassB class]);
	//WHEN
	@try {
	[strictMock executeVoidMethodAndException:@"@congpc.ios"];// this will throw an exception
	}
	@catch (NSException *exception) {
	NSLog(@"%@",exception);
	}
	@finally {
	NSLog(@"Final");
	}
	//THEN
	OCMVerify([strictMock executeVoidMethodAndException:@"@congpc.ios"]);
	XCTAssertThrows([strictMock executeVoidMethodAndException:@"@congpc.ios"]);// this will throw an exception
	}
	- (void)testException_UsingClassMockAndThrow {
	//GIVEN
	//Change NSGenericException to NSRangeException and run again.
	NSException* anException = [NSException exceptionWithName:NSGenericException reason:@"" userInfo:nil];
	ClassA* object = [[ClassA alloc] init];
	id classMock = OCMClassMock([ClassB class]);
	OCMStub([classMock executeVoidMethod]).andThrow(anException);
	object->publicClass = classMock;
	//WHEN + THEN
	XCTAssertThrowsSpecificNamed([object executeVoidMethodAndSubVoidMethod], NSException, NSGenericException);
	}

view raw Exception hosted with ❤ by GitHub

• 10. Advanced topics

Verifying in order:The mock can be told to verify that expected methods are called in the same order as the expectations are set up. As soon as a method is called that is not next on the “expected list” the mock will fail fast and throw an exception.

	- (void)testVerifyingInOrder_UsingStrictMock {
	//GIVEN
	id strictMock = OCMStrictClassMock([ClassB class]);
	[strictMock setExpectationOrderMatters:YES];
	//WHEN
	OCMExpect([strictMock executeMethodWithOrder1]); // First
	OCMExpect([strictMock executeMethodWithOrder2]); // Second
	//THEN
	[strictMock executeMethodWithOrder1];//Comment this code and run again.
	// calling executeMethodWithOrder2 before executeMethodWithOrder1 will cause an exception to be thrown
	[strictMock executeMethodWithOrder2];
	}

view raw VerifyingInOrder hosted with ❤ by GitHub

Using reject method:

	- (void)testRejectActions_UsingClassMock {
	//GIVEN
	ClassA* object = [[ClassA alloc] init];
	id classMock = OCMClassMock([ClassB class]);
	[[classMock reject] executeReturnMethod];
	object->publicClass = classMock;
	//WHEN + THEN
	[object executeRejectMethod];
	}
	- (void)testRejectActions_UsingPartialMock {
	//GIVEN
	ClassB* object = [[ClassB alloc] init];
	id classMock = OCMPartialMock(object);
	[[classMock reject] executeReturnMethod];
	//WHEN + THEN
	[object executeRejectMethod];
	}

view raw RejectAction hosted with ❤ by GitHub

Using expect and return:

	- (void)testStubActionsAndExpect_UsingClassMock {
	//GIVEN
	ClassA* object = [[ClassA alloc] init];
	id classMock = OCMClassMock([ClassB class]);
	OCMExpect([classMock executeReturnMethod]).andReturn(@"@congpc.ios");
	object->publicClass = classMock;
	//WHEN /* run code under test */
	[object executeVoidMethodAndReturnMethod];
	//THEN
	OCMVerifyAll(classMock);
	}

view raw ExpectAndReturn hosted with ❤ by GitHub

Test to open an url:

	- (void)testOpenUrl {
	ViewController *toTest = [[ViewController alloc] init];
	NSURL *toOpen = [NSURL URLWithString:@"http://www.google.com"];
	// Create a partial mock of UIApplication
	id mockApplication = [OCMockObject partialMockForObject:[UIApplication sharedApplication]];
	// Set an expectation that the UIApplication will be told to open the url
	[[mockApplication expect] openURL:toOpen];
	[toTest launchURL:toOpen]; //Test private method
	[mockApplication verify];
	[mockApplication stopMocking];
	}

view raw OpenURL hosted with ❤ by GitHub

Tools: XCode 7, OCMock 3.0

Reference documents:

- OCMock
- Engineering
- StackOverflow