Create a Test Target

With the test navigator open, click the Add button (+) in the bottom-left corner and choose New Unit Test Target from the menu.

Pick the macOS or iOS Unit Testing Bundle from the next dialog and click Next. In the new target setup assistant that appears, edit the Product Name and other parameters to your preferences and needs.

Click Finish to add your target, which contains a template test class and two test method templates, to the test navigator view.

Run the Test and See the Results

Now that you’ve added testing to your project, you want to develop the tests to do something useful. But first, hold the pointer over the SampleCalcTests test class in the test navigator and click the Run button to run all the test methods in the class. The results are indicated by the green checkmarks next to the function names and in the source editor gutter.

The template unit and performance tests are both empty, which is why they post success indications; no failure was asserted. Notice the gray diamond on line 34 in the figure at the measureBlock: method. Clicking this diamond displays the Performance Result panel.

This panel allows you to set a performance baseline as well as edit the baseline and Max STDDEV parameters. These features will be discussed later.

Edit the Tests and Run Again

Because this sample project is a calculator app, you want to check whether it performs the operations of addition, subtraction, multiplication, and division correctly, as well as test other calculator functions. Because tests are built in the app project, you can add all the context and other information needed to perform tests at whatever level of complexity makes sense for your needs. Creating tests is a matter of adding methods to the unit tests implementation file.

For example, you insert the following #import and instance variable declarations into the SampleCalcTests.m file.

#import <XCTest/XCTest.h>

//

// Import the application specific header files

#import "CalcViewController.h"

#import "CalcAppDelegate.h"

@interface CalcTests : XCTestCase {

// add instance variables to the CalcTests class

@private

    NSApplication       *app;

    CalcAppDelegate     *appDelegate;

    CalcViewController  *calcViewController;

    NSView              *calcView;

}

@end

Then give the test method a descriptive name, such as testAddition, and add the implementation source for the method.

- (void) testAddition

{

   // obtain the app variables for test access

   app                  = [NSApplication sharedApplication];

   calcViewController   = (CalcViewController*)[[NSApplication sharedApplication] delegate];

   calcView             = calcViewController.view;

   // perform two addition tests

   [calcViewController press:[calcView viewWithTag: 6]];  // 6

   [calcViewController press:[calcView viewWithTag:13]];  // +

   [calcViewController press:[calcView viewWithTag: 2]];  // 2

   [calcViewController press:[calcView viewWithTag:12]];  // =

    XCTAssertEqualObjects([calcViewController.displayField stringValue], @"8", @"Part 1 failed.");

   [calcViewController press:[calcView viewWithTag:13]];  // +

   [calcViewController press:[calcView viewWithTag: 2]];  // 2

   [calcViewController press:[calcView viewWithTag:12]];  // =

    XCTAssertEqualObjects([calcViewController.displayField stringValue], @"10", @"Part 2 failed.");

}

Notice that the list in the test navigator changed to reflect that the sample test method, testExample, has been replaced by testAddition.

Now use the Run button in the test navigator (or the indicator in the source editor) to run the testAddition method.

As you can see, an assertion failed and is highlighted in the test navigator and the source editor. Looking at the source, Part 1 succeeded—it is Part 2 that has a problem. On closer examination, the error is obvious: In line 76, [calcView viewWithTag:11] is off by one, it should be [calcView viewWithTag:12]. Correcting this error fixes the problem and the test succeeds.

Use the setUp() and tearDown() Methods for Common Code

Xcode runs test methods one at a time for all the test classes in the active test bundle. In this small example only the one test method was implemented in the test class, and it needed access to three of the calculator app variable objects to function. If you wrote four or five test methods in this same class, you might find yourself repeating the same code in every test method to obtain access to the app object state. The XCTest framework provides you with instance methods for test classes, setUp and tearDown, which you can use to put such common code called before and after runs each test method runs.

Using setUp and tearDown is simple. From the testAddition source in Mac_Calc_Tests.m, cut the four lines starting with // obtain the app variable for test access and paste them into the default setUp instance method provided by the template.

- (void)setUp

{

    [super setUp];

    // Put setup code here. This method is called before the invocation of each test method in the class.

   // obtain the app variables for test access

   app                  = [NSApplication sharedApplication];

   calcViewController   = (CalcViewController*)[[NSApplication sharedApplication] delegate];

   calcView             = calcViewController.view;

}

Now add more test methods—testSubtraction and others—with minimal duplicated code.