iOS 单元测试之XCTest详解(一)

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前言:测试是一个好的App不可缺少的部分。每一个App都是由一个个小的功能组合到一起的。而这些小的功能又是由一个个函数或者说算法组合到一起的。单元测试就是对这些小的功能或者函数进行测试,良好的单元测试会让代码的健壮性提高很多。XCTest就是XCode为我们提供的一个框架,它提供了各个层次的测试。

XCTestCase

每个XCode创建iOS的工程中都有一个叫做”工程名Tests”的分组,这个分组里就是XCTestCase的子类,XCTest中的测试类都是继承自XCTestCase。
例如新建一个工程,命名为Demo,就能看到如图
iOS 单元测试之XCTest详解(一)_第1张图片
看一下这个自动创建的文件里都包含了哪些内容

#import <UIKit/UIKit.h>
#import <XCTest/XCTest.h>

@interface DemoTests : XCTestCase

@end

@implementation DemoTests

- (void)setUp {
    [super setUp];
    // Put setup code here. This method is called before the invocation of each test method in the class.
}

- (void)tearDown {
    // Put teardown code here. This method is called after the invocation of each test method in the class.
    [super tearDown];
}

- (void)testExample {
    // This is an example of a functional test case.
    XCTAssert(YES, @"Pass");
}

- (void)testPerformanceExample {
    // This is an example of a performance test case.
    [self measureBlock:^{
        // Put the code you want to measure the time of here.
    }];
}

@end

测试用例的命名

XCTest中所有的测试用例的命名都是以test开头的。例如上文中的

- (void)testExample {
    // This is an example of a functional test case.
    XCTAssert(YES, @"Pass");
}

setUp和tearDown

Setup是在所有测试用例运行之前运行的函数,在这个测试用例里进行一些通用的初始化工作

tearDown是在所有的测试用例都执行完毕后执行的

XCode的测试用例导航

测试用例的导航如图,在测试用例的导航里,我们可以运行一组测试用例,也可以运行一个单独的测试用例

可以鼠标右键来新建一组测试用例。

也可以为测试用例添加失败断点来方便我们调试
iOS 单元测试之XCTest详解(一)_第2张图片

普通方法测试

例如,新建一个类命名为Model,他有这个方法用来生成10以内的随机数。

-(NSInteger)randomLessThanTen{ return arc4random()%10; }

于是,测试方法为

-(void)testModelFunc_randomLessThanTen{ Model * model = [[Model alloc] init]; NSInteger num = [model randomLessThanTen]; XCTAssert(num<10,@"num should less than 10"); }

我们点击如图的左边图标单独运行这个测试用例,当然也可以在上文我提到的导航栏里单独运行。
iOS 单元测试之XCTest详解(一)_第3张图片
然后会看到输出表示这个测试用例通过

Test Suite 'Selected tests' started at 2015-06-28 05:24:56 +0000
Test Suite 'DemoTests.xctest' started at 2015-06-28 05:24:56 +0000
Test Suite 'DemoTests' started at 2015-06-28 05:24:56 +0000
Test Case '-[DemoTests testModelFunc_randomLessThanTen]' started.
Test Case '-[DemoTests testModelFunc_randomLessThanTen]' passed (0.000 seconds).
Test Suite 'DemoTests' passed at 2015-06-28 05:24:56 +0000.
     Executed 1 test, with 0 failures (0 unexpected) in 0.000 (0.001) seconds
Test Suite 'DemoTests.xctest' passed at 2015-06-28 05:24:56 +0000.
     Executed 1 test, with 0 failures (0 unexpected) in 0.000 (0.001) seconds
Test Suite 'Selected tests' passed at 2015-06-28 05:24:56 +0000.

常用断言

如何判断一个测试用例成功或者失败呢?XCTest使用断言来实现。
最基本的断言
表示如果expression满足,则测试通过,否则对应format的错误。

XCTAssert(expression, format...)

还有一个用来直接Fail的断言

XCTFail(format...)

其他一些常用的断言:

XCTAssertTrue(expression, format...)
XCTAssertFalse(expression, format...)
XCTAssertEqual(expression1, expression2, format...)
XCTAssertNotEqual(expression1, expression2, format...)
XCTAssertEqualWithAccuracy(expression1, expression2, accuracy, format...)
XCTAssertNotEqualWithAccuracy(expression1, expression2, accuracy, format...)
XCTAssertNil(expression, format...)
XCTAssertNotNil(expression, format...)

性能测试

所谓性能测试,主要就是评估一段代码的运行时间,XCTest的性能的测试利用如下格式

- (void)testPerformanceExample {
    // This is an example of a performance test case.
    [self measureBlock:^{
        // Put the code you want to measure the time of here.
    }];
}

例如,我要评估一段代码,这段代码的功能是把一张图片缩小到指定的大小。
这段代码如下,这段代码我放在UIImage的类别里。

+ (UIImage*)imageWithImage:(UIImage*)image
              scaledToSize:(CGSize)newSize
{
    UIGraphicsBeginImageContext( newSize );
    [image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return newImage;
}

然后测试用例如图,主要判断resize后是否为nil,并且尺寸是否对。

- (void)testPerformanceExample {
    UIImage * image = [UIImage imageNamed:@"icon.png"];
    [self measureBlock:^{
        UIImage * resizedImage = [UIImage imageWithImage:image scaledToSize:CGSizeMake(100, 100)];
        XCTAssertNotNil(resizedImage,@"resized image should not be nil");
        CGFloat resizedWidth = resizedImage.size.width;
        CGFloat resizedHeight = resizedImage.size.height;
        XCTAssert(resizedHeight == 100 && resizedWidth == 100,@"Size is not right");
    }];
}

输出

Test Suite 'Selected tests' started at 2015-06-28 05:42:39 +0000
Test Suite 'DemoTests.xctest' started at 2015-06-28 05:42:39 +0000
Test Suite 'DemoTests' started at 2015-06-28 05:42:39 +0000
Test Case '-[DemoTests testPerformanceExample]' started.
/Users/huangwenchen/Desktop/Demo/DemoTests/DemoTests.m:41: Test Case '-[DemoTests testPerformanceExample]' measured [Time, seconds] average: 0.000, relative standard deviation: 40.714%, values: [0.000241, 0.000116, 0.000128, 0.000089, 0.000087, 0.000081, 0.000101, 0.000093, 0.000092, 0.000087], performanceMetricID:com.apple.XCTPerformanceMetric_WallClockTime, baselineName: "", baselineAverage: , maxPercentRegression: 10.000%, maxPercentRelativeStandardDeviation: 10.000%, maxRegression: 0.100, maxStandardDeviation: 0.100
Test Case '-[DemoTests testPerformanceExample]' passed (0.357 seconds).
Test Suite 'DemoTests' passed at 2015-06-28 05:42:40 +0000.
     Executed 1 test, with 0 failures (0 unexpected) in 0.357 (0.358) seconds
Test Suite 'DemoTests.xctest' passed at 2015-06-28 05:42:40 +0000.
     Executed 1 test, with 0 failures (0 unexpected) in 0.357 (0.358) seconds
Test Suite 'Selected tests' passed at 2015-06-28 05:42:40 +0000.
     Executed 1 test, with 0 failures (0 unexpected) in 0.357 (0.360) seconds

异步测试

异步测试的逻辑如下,首先定义一个或者多个XCTestExpectation,表示异步测试想要的结果。然后设置timeout,表示异步测试最多可以执行的时间。最后,在异步的代码完成的最后,调用fullfill来通知异步测试满足条件。

- (void)testAsyncFunction{
    XCTestExpectation * expectation = [self expectationWithDescription:@"Just a demo expectation,should pass"];
    //Async function when finished call [expectation fullfill]
    [self waitForExpectationsWithTimeout:10 handler:^(NSError *error) {
        //Do something when time out
    }];
}

举例

- (void)testAsyncFunction{
    XCTestExpectation * expectation = [self expectationWithDescription:@"Just a demo expectation,should pass"];
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        sleep(1);
        NSLog(@"Async test");
        XCTAssert(YES,"should pass");
        [expectation fulfill];
    });
    [self waitForExpectationsWithTimeout:10 handler:^(NSError *error) {
        //Do something when time out
    }];
}

测试结果

Test Suite 'Selected tests' started at 2015-06-28 05:49:43 +0000
Test Suite 'DemoTests.xctest' started at 2015-06-28 05:49:43 +0000
Test Suite 'DemoTests' started at 2015-06-28 05:49:43 +0000
Test Case '-[DemoTests testAsyncFunction]' started.
2015-06-28 13:49:44.920 Demo[2157:145428] Async test
Test Case '-[DemoTests testAsyncFunction]' passed (1.006 seconds).
Test Suite 'DemoTests' passed at 2015-06-28 05:49:44 +0000.
     Executed 1 test, with 0 failures (0 unexpected) in 1.006 (1.007) seconds
Test Suite 'DemoTests.xctest' passed at 2015-06-28 05:49:44 +0000.
     Executed 1 test, with 0 failures (0 unexpected) in 1.006 (1.009) seconds
Test Suite 'Selected tests' passed at 2015-06-28 05:49:44 +0000.

后续:

计划下一篇会讲解Mock 测试以及一些常用的Mock小工具。

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