Based on instructions from here http://ocmock.org/

Down here http://ocmock.org/download/ and extract to somewhere into your project like this.

Screen Shot 2015-09-25 at 8.47.50 AM

Then follow instructions here http://ocmock.org/ios/

Add the library
Screen Shot 2015-09-25 at 8.49.19 AM

Set the linker flags
Screen Shot 2015-09-25 at 8.51.08 AM

Make headers available
Screen Shot 2015-09-25 at 8.50.22 AM

Add code

#import <XCTest/XCTest.h>
#import <OCMock/OCMock.h>
#import "TaxCalculator.h"
#import "SubscriptionManager.h"

@interface TaxCalculatorTest : XCTestCase
@property (nonatomic, strong) TaxCalculator *calculator;
@end

@implementation TaxCalculatorTest

- (void)setUp {
    [super setUp];
    self.calculator = [TaxCalculator new];
}

- (void)testExample {
    XCTAssertEqual(0, [self.calculator calculateTax]);
    id mockSubscriptionManager = OCMClassMock([SubscriptionManager class]);
}

@end