iOS 单元測试之XCTest具体解释（一）[通俗易懂]

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前言：測试是一个好的App必不可少的部分。每个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。单元測试就是对这些小的功能或者函数进行測试，良好的单元測试会让代码的健壮性提高非常多。XCTest就是XCode为我们提供的一个框架，它提供了各个层次的測试。

XCTestCase

每个XCode创建iOS的project中都有一个叫做”project名Tests”的分组，这个分组里就是XCTestCase的子类。XCTest中的測试类都是继承自XCTestCase。
比如新建一个project，命名为Demo。就能看到如图

看一下这个自己主动创建的文件中都包括了哪些内容

#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

測试用例的命名

XCTest中全部的測试用例的命名都是以test开头的。比如上文中的

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

setUp和tearDown

Setup是在全部測试用例执行之前执行的函数，在这个測试用例里进行一些通用的初始化工作

tearDown是在全部的測试用例都执行完毕后执行的

XCode的測试用例导航

測试用例的导航如图。在測试用例的导航里，我们能够执行一组測试用例，也能够执行一个单独的測试用例

能够鼠标右键来新建一组測试用例。

也能够为測试用例加入失败断点来方便我们调试

普通方法測试

比如，新建一个类命名为Model，他有这种方法用来生成10以内的随机数。

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

于是。測试方法为

-(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执行这个測试用例，当然也能够在上文我提到的导航栏里单独执行。

然后会看到输出表示这个測试用例通过

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.

经常使用断言

怎样推断一个測试用例成功或者失败呢？XCTest使用断言来实现。
最主要的断言
表示假设expression满足。则測试通过，否则相应format的错误。

XCTAssert(expression, format...)

另一个用来直接Fail的断言

XCTFail(format...)

其它一些经常使用的断言：

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...)

性能測试

所谓性能測试，主要就是评估一段代码的执行时间，XCTest的性能的測试利用例如以下格式

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

比如。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。

这段代码例如以下，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;
}

然后測试用比如图，主要推断resize后是否为nil。而且尺寸是否对。

- (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

异步測试

异步測试的逻辑例如以下。首先定义一个或者多个XCTestExpectation。表示异步測试想要的结果。然后设置timeout，表示异步測试最多能够执行的时间。

最后，在异步的代码完毕的最后。调用fullfill来通知异步測试满足条件。

- (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
    }];
}

測试结果

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.

兴许：

计划下一篇会解说Mock 測试以及一些经常使用的Mock小工具。