Unit testing using Xcode

Testing a block of code or some method:

• Import the class, which contains the method to be tested.
• Perform the operation with dummy data.
• Now compare the result of operation with expected result.

- (void)testReverseString{
NSString *originalString = @"hi_my_name_is_siddharth";
NSString *reversedString = [self.someObject reverseString:originalString];
NSString *expectedReversedString = @"htrahddis_si_eman_ym_ih";
XCTAssertEqualObjects(expectedReversedString, reversedString, @"The reversed string did not match the expected reverse");
}

Feed the dummy data to the method under test if required & then compare the expected & actual results.

Testing asynchronous block of code:

- (void)testDoSomethingThatTakesSomeTime{
XCTestExpectation *completionExpectation = [self expectationWithDescription:@"Long method"];
[self.someObject doSomethingThatTakesSomeTimesWithCompletionBlock:^(NSString *result) {
    XCTAssertEqualObjects(@"result", result, @"Result was not correct!");
    [completionExpectation fulfill];
}];
[self waitForExpectationsWithTimeout:5.0 handler:nil];
}

• Feed the dummy data to the method under test if required.
• The test will pause here, running the run loop, until the timeout is hit or all expectations are fulfilled.
• Timeout is the expected time for the asynchronous block to response.

Measuring Performance of a block of code:

1. For Synchronous methods :

- (void)testPerformanceReverseString {
    NSString *originalString = @"hi_my_name_is_siddharth";
    [self measureBlock:^{
        [self.someObject reverseString:originalString];
    }];
}

2. For Asynchronous methods :

- (void)testPerformanceOfAsynchronousBlock {
   [self measureMetrics:@[XCTPerformanceMetric_WallClockTime] automaticallyStartMeasuring:YES forBlock:^{

    XCTestExpectation *expectation = [self expectationWithDescription:@"performanceTestWithResponse"];

    [self.someObject doSomethingThatTakesSomeTimesWithCompletionBlock:^(NSString *result) {
        [expectation fulfill];
    }];
    [self waitForExpectationsWithTimeout:5.0 handler:^(NSError *error) {
    }];
}];
}

• These performance measure block gets executed for 10 times consecutively & then the average is calculated, & on the basis of this average performance result gets created & baseline is accepted for further evaluation.
• The performance result is compared with the previous test results & baseline with a customizable max standard deviation.

Running Test Suits:

Run all tests by choosing Product > Test. Click the Test Navigator icon to view the status and results of the tests. You can add a test target to a project (or add a class to a test) by clicking the Add (plus) button in the bottom-left corner of the test navigator. To view the source code for a particular test, select it from the test list. The file opens in the source code editor.

Note:

Make sure that include unit test case box is checked when creating a new project as shown below:

Remarks

Dependencies:

• If application uses third party libraries or cocoa pods, then those libraries or pods are needed to be install for test as well.
• Test class (Test Suit) extends XCTestCase.

Get brushed up before starting:

All test classes have two methods in common setUp & tearDown.

setUp runs before every testcase & tearDown after every testcase.

Test cases runs alphabetically.

In Test Driven Development, it is good to create dummy test data first.

Test case methods starts with "test" keyword.

Test methods accept no parameters & return no value.

Appendix:

There are several other methods for comparing the expected result & actual result out of an operation. Some of those methods are listed below:

• XCTAssertNil(expression, comment) generates a failure if expression != nil.
• XCTAssertNotNil(expression, comment) generates a failure if expression = nil.
• XCTAssert(expression, comment) generates a failure if expression == false.
• XCTAssertTrue(expression, comment) generates a failure if expression == false.
• XCTAssertFalse(expression, comment) generates a failure if expression != false.
• XCTAssertEqualObjects(expression1, expression2, comment) generates a failure if expression1 is not equal to expression2.
• XCTAssertEqualObjects(expression1, expression2, comment) generates a failure if expression1 is equal to expression2.
• XCTAssertNotEqual(expression1, expression2, comment) generates a failure if expression1 == expression2.
• XCTAssertEqual(expression1, expression2, comment) generates a failure if expression1 != expression2.
• XCTAssertGreaterThanOrEqual(expression1, expression2, comment) generates a failure when ( expression1 < expression2).