iOS 单元测试之XCTest详解（一）

iOS 单元测试之XCTest详解（一）

http://blog.csdn.net/hello_hwc/article/details/46671053

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http://blog.csdn.net/column/details/huangwenchen-ios-sdk.html

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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;
}

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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");
}

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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 +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.

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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...)

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还有一个用来直接Fail的断言

XCTFail(format...)

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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.
    }];
}

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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;
}

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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");
    }];
}

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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

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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
    }];
}

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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
    }];
}

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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.