iOS 单元测试之XCTest详解（一），iosxctest

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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。

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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

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

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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");}

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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

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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

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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。

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 +0000Test Suite 'DemoTests.xctest' started at 2015-06-28 05:24:56 +0000Test Suite 'DemoTests' started at 2015-06-28 05:24:56 +0000Test 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) secondsTest 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) secondsTest Suite 'Selected tests' passed at 2015-06-28 05:24:56 +0000.

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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...)

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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 +0000Test Suite 'DemoTests.xctest' started at 2015-06-28 05:42:39 +0000Test Suite 'DemoTests' started at 2015-06-28 05:42:39 +0000Test 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: 0.100Test 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) secondsTest 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) secondsTest 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

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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 +0000Test Suite 'DemoTests.xctest' started at 2015-06-28 05:49:43 +0000Test Suite 'DemoTests' started at 2015-06-28 05:49:43 +0000Test Case '-[DemoTests testAsyncFunction]' started.2015-06-28 13:49:44.920 Demo[2157:145428] Async testTest 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) secondsTest 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) secondsTest Suite 'Selected tests' passed at 2015-06-28 05:49:44 +0000.

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后续：

计划下一篇会讲解Mock 测试以及一些常用的Mock小工具。