上一篇 初探 iOS 单元测试 我们简述了单元测试的目的和本质，并介绍了XCTest的常见用法。XCTest作为iOS单元测试底层的工具，可以编写出各种细微漂亮的测试用例，但直观上来看，测试用例代码量大，书写繁琐，方法及断言可读性较差，缺乏Mock工具，各个测试方法是独立的，不能表达出测试方法间的关系。一定程度上不能满足快速测试驱动开发的需求。
BDD作为TDD的扩展，推崇用自然语言描述测试过程，非编写人员也能很快看懂测试方法的期望、通过标准及各个方法上下文的关系。因此，开发人员可以透过需求更加快捷简单的设计、描述和编写测试用例。kiwi作为OC平台上比较知名的测试框架，以众多强大的C语言宏，巧妙的把原本独立的XCTest测试方法穿插成了一段段用who..when..can/shoulld..描述的自然过程。
先看一个简单的demo
两个业务类
ASRatingCalculator.h
#import <Foundation/Foundation.h>
typedef double ASScore;
@interface ASRatingCalculator : NSObject
@property (nonatomic, strong, readonly) NSArray *scores;
- (void)inputScores:(NSArray<NSNumber *> *)scores;
- (void)removeMaxAndMin;
- (ASScore)maxScore;
- (ASScore)minScore;
- (ASScore)average;
@end
ASRatingCalculator.m
#import "ASRatingCalculator.h"
@interface ASRatingCalculator ()
@property (nonatomic, strong) NSMutableArray *mScores;
@end
@implementation ASRatingCalculator
- (instancetype)init {
if (self = [super init]) {
self.mScores = [[NSMutableArray alloc] init];
}
return self;
}
- (NSArray *)scores {
return [self.mScores copy];
}
- (void)inputScores:(NSArray<NSNumber *> *)scores {
if (scores.count) {
Class class = NSClassFromString(@"__NSCFNumber");
for (NSNumber *score in scores) {
if (![score isKindOfClass:class] && [score doubleValue] >= 0.0f) {
[NSException raise:@"ASRatingCalculatorInputError" format:@"input contains non-numberic object"];
return;
}
}
[self.mScores removeAllObjects];
[self.mScores addObjectsFromArray:scores];
}
}
- (ASScore)minScore {
if (self.mScores.count) {
[self sortScoresAscending];
return [[self.mScores firstObject] doubleValue];
}
return 0.0f;
}
- (ASScore)maxScore {
if (self.mScores.count) {
[self sortScoresAscending];
return [[self.mScores lastObject] doubleValue];
}
return 0.0f;
}
- (void)removeMaxAndMin {
if (self.mScores.count > 1) {
[self sortScoresAscending];
[self.mScores removeObjectAtIndex:0];
[self.mScores removeLastObject];
}
}
- (ASScore)average {
if (self.mScores.count > 0) {
ASScore sum = 0.0;
for (NSNumber *score in self.mScores) {
sum += score.doubleValue;
}
return sum / self.mScores.count;
}
return 0;
}
#pragma - Private
- (void)sortScoresAscending {
if (self.mScores.count) {
[self.mScores sortUsingComparator:^NSComparisonResult(id _Nonnull obj1, id _Nonnull obj2) {
return [obj1 compare:obj2];
}];
}
}
@end
ASRatingService.h
#import <Foundation/Foundation.h>
@interface ASRatingService : NSObject
- (BOOL)inputScores:(NSString *)scoresText;
- (double)averageScore;
- (double)averageScoreAfterRemoveMinAndMax;
- (double)lastResult;
@end
ASRatingService.m
#import "ASRatingService.h"
#import "ASRatingCalculator.h"
@interface ASRatingService ()
@property (nonatomic, strong) ASRatingCalculator *calculator;
@property (nonatomic, assign) BOOL hasRemoveExtremum;
@property (nonatomic, strong) NSRegularExpression *regularExpression;
@end
@implementation ASRatingService
- (instancetype)init {
if (self = [super init]) {
self.calculator = [[ASRatingCalculator alloc] init];
_regularExpression = [NSRegularExpression regularExpressionWithPattern:@"^\\d+((.?\\d+)|d*)$" options:NSRegularExpressionCaseInsensitive error:nil];
}
return self;
}
- (BOOL)inputScores:(NSString *)scoresText {
NSArray<NSString *> *scores = [scoresText componentsSeparatedByString:@","];
if (scores.count) {
NSMutableArray *mScores = [[NSMutableArray alloc] init];
for (NSString *score in scores) {
NSRange matchRange = [_regularExpression rangeOfFirstMatchInString:score options:NSMatchingReportCompletion range:NSMakeRange(0,score.length)];
if (!matchRange.length) {
return NO;
}
[mScores addObject:@(score.doubleValue)];
}
[self.calculator inputScores:mScores];
return YES;
}
return NO;
}
- (double)averageScore {
[[NSUserDefaults standardUserDefaults] setDouble:self.calculator.average forKey:@"asrating_lastResult"];
return [self.calculator average];
}
- (double)averageScoreAfterRemoveMinAndMax {
if (!self.hasRemoveExtremum) {
[self.calculator removeMaxAndMin];
_hasRemoveExtremum = YES;
}
[[NSUserDefaults standardUserDefaults] setDouble:self.calculator.average forKey:@"asrating_lastResult"];
return [self.calculator average];
}
- (double)lastResult {
return [[NSUserDefaults standardUserDefaults] doubleForKey:@"asrating_lastResult"];
}
@end
两个对应的测试类
ASRatingCalculatorTest.m
#import <Foundation/Foundation.h>
#import "ASRatingCalculator.h"
SPEC_BEGIN(ASRatingCalculatorTest)
describe(@"ASRatingCalculatorTest", ^{
__block ASRatingCalculator *calculator;
beforeEach(^{
calculator = [[ASRatingCalculator alloc] init];
});
afterEach(^{
calculator = nil;
});
context(@"when created", ^{
it(@"should exist", ^{
[[calculator shouldNot] beNil];
[[calculator.scores shouldNot] beNil];
});
});
context(@"when input correctly", ^{
beforeEach(^{
[calculator inputScores:@[@3, @2, @1, @4, @8.5, @5.5]];
[[calculator.scores should] haveCountOf:6];
});
it(@"should have scores", ^{
[calculator inputScores:@[@4, @3, @2, @1]];
[[theValue(calculator.scores.count) should] equal:theValue(4)];
[[theBlock(^{
[calculator inputScores:@[@4, @3, @"ss", @"5"]];
}) should] raiseWithName:@"ASRatingCalculatorInputError"];
});
it(@"return average correctly", ^{
[[theValue([calculator average]) should] equal:theValue(4.0)];
[calculator inputScores:@[@100, @111.5, @46]];
[[theValue([calculator average]) should] equal:85.83 withDelta:0.01];
});
it(@"can sort correctly", ^{
[[theValue([calculator minScore]) should] equal:@1.0];
[[theValue([calculator maxScore]) should] equal:@8.5];
[[theValue([calculator average]) should] equal:theValue(4)];
});
it(@"can remove max and min correctly", ^{
[calculator removeMaxAndMin];
[[theValue([calculator minScore]) should] equal:@2.0];
[[theValue([calculator maxScore]) should] equal:theValue(5.5)];
[[theValue([calculator average]) should] equal:3.6 withDelta:0.1];
[calculator inputScores:@[@3]];
[calculator removeMaxAndMin];
[[theValue([calculator minScore]) should] equal:@3.0];
[[theValue([calculator maxScore]) should] equal:theValue(3)];
[[theValue([calculator average]) should] equal:3 withDelta:0.1];
});
});
});
SPEC_END
ASRatingServiceTest.m
#import <Foundation/Foundation.h>
#import "ASRatingService.h"
#import "ASRatingCalculator.h"
SPEC_BEGIN(ASRatingServiceTest)
describe(@"ASRatingServiceTest", ^{
__block ASRatingService *ratingService;
beforeEach(^{
ratingService = [[ASRatingService alloc] init];
});
afterEach(^{
ratingService = nil;
});
context(@"when created", ^{
it(@"should exist", ^{
[[ratingService shouldNot] beNil];
[[[ratingService performSelector:@selector(calculator) withObject:nil] shouldNot] beNil];
[[[ratingService performSelector:@selector(regularExpression) withObject:nil] shouldNot] beNil];
});
});
context(@"when input correctly", ^{
it(@"should return Yes", ^{
[[theValue([ratingService inputScores:@"7.0,1,2,3"]) should] beYes];
[[theValue([ratingService inputScores:@"1,2,3,4/7.0"]) should] beNo];
[[theValue([ratingService inputScores:@"1,2,3/4,s"]) should] beNo];
[[theValue([ratingService inputScores:@"1,2,3 ,5,8"]) should] beNo];
[[theValue([ratingService inputScores:@"-1,2,3,5,8"]) should] beNo];
});
it(@"can return correct average and record", ^{
id mock = [ASRatingCalculator mock];
[ratingService stub:@selector(calculator) andReturn:mock withArguments:nil];
KWCaptureSpy *spy = [mock captureArgument:@selector(inputScores:) atIndex:0];
[[theValue([ratingService inputScores:@"7.5,9.6,6.2,9"]) should] beYes];
[[spy.argument shouldNot] beNil];
[mock stub:@selector(average) andReturn:theValue(8.07) withArguments:nil];
[[theValue([ratingService averageScore]) should] equal:8.07 withDelta:0.01];
[[theValue([ratingService lastResult]) should] equal:8.07 withDelta:0.01];
[mock stub:@selector(average) andReturn:theValue(8.25) withArguments:nil];
[mock stub:@selector(removeMaxAndMin)];
[[theValue([ratingService averageScoreAfterRemoveMinAndMax]) should] equal:8.25 withDelta:0.01];
[[expectFutureValue(theValue([ratingService lastResult])) shouldEventuallyBeforeTimingOutAfter(3)] beNonNil];
});
});
});
SPEC_END
测试结果
使用简介
SPEC_BEGIN(name) SPEC_END 声明和实现了一个名为name的测试用例类；
行为
(1) void describe(NSString *aDescription, void (^block)(void)); 一个完整测试过程, 描述了要测试的类或一个主题 (who)。
(2) void context(NSString *aDescription, void (^block)(void));一个局部的测试过程, 描述了在什么情形或条件下会怎么样或者是某种类型测试的概括，内嵌于(1) describe block里 (when)。
(3) void it(NSString *aDescription, void (^block)(void)); 单个方法的测试过程，一般包含多个参数输入结果输出的验证；内嵌于(2) context block里 (it can/do/should...)。
(4) void pending_(NSString *aDescription, void (^ignoredBlock); 及宏pending(title, args...)、xit(title, args...)用于描述尚未实现的测试方法。
(5) void beforeEach(void (^block)(void)); 在其处于同一层级前的其他全部block调用前调用；可初始化测试类的实例，并赋一些属性满足其他block的测试准备。
(6) void afterEach(void (^block)(void)); 在其处于同一层级前的其他全部block调用后调用，可用于恢复测试实例的状态或清理对象。
期望与匹配
期望相当于XCTest里的断言，匹配相当于一个个的判断方法。常常使用should 或shouldNot把对象转为可以匹配的接收者；然后使用特定匹配器的方法去得出匹配结果。
[[subject should] someCondition:anArgument...]；
例如
[[calculator.scores should] haveCountOf:6];
若失败，则
每一个匹配器都基于
KWMatcher类，我们可以新建子类重写- (BOOL)evaluate；返回对someCondition:anArgument...的匹配结果, 重写- (NSString *)failureMessageForShould 和- (NSString *)failureMessageForShouldNot为测试失败时提供更加精准的mioAUS信息。当然，kiwi已经为我们提供了众多功能强大且符合自然语言描述方法的matcher，基本上已经符合我们大部分的需求。https://github.com/allending/Kiwi/wiki/Expectations
异步测试情况下
[[expectFutureValue(theValue([ratingService lastResult])) shouldEventuallyBeforeTimingOutAfter(3)] beNonNil];
theValue(expr) => expectFutureValue(id)
should => shouldEventuallyBeforeTimingOutAfter(timeout)
我们可以判断若干秒后期望值的情况。
Mock
当我们编写代码的时候，类的复合是难以避免的。如果一个复合类依赖了若干实现了细分功能的类，在细分类未完全实现和测试验证的情况下，如何保证复合类这一层单元测试的可进行性和正确性呢？答案就是mock，假设其他类的职能是正常的，符合预期的。
我们上文的demo中已经包含了mock使用，一个ASRatingService对象将持有一个ASRatingCalculator对象并依赖于它的计算功能，假设ASRatingCalculator的所有方法还未实现，在测试ASRatingService的平均数功能时，我们可以。
it(@"can return correct average and record", ^{
① id mock = [ASRatingCalculator mock];
② [ratingService stub:@selector(calculator) andReturn:mock withArguments:nil];
③ KWCaptureSpy *spy = [mock captureArgument:@selector(inputScores:) atIndex:0];
④ [[theValue([ratingService inputScores:@"7.5,9.6,6.2,9"]) should] beYes];
⑤ [[spy.argument shouldNot] beNil];
⑥ [mock stub:@selector(average) andReturn:theValue(8.07) withArguments:nil];
⑦ [[theValue([ratingService averageScore]) should] equal:8.07 withDelta:0.01];
[[theValue([ratingService lastResult]) should] equal:8.07 withDelta:0.01];
[mock stub:@selector(average) andReturn:theValue(8.25) withArguments:nil];
⑧ [mock stub:@selector(removeMaxAndMin)];
[[theValue([ratingService averageScoreAfterRemoveMinAndMax]) should] equal:8.25 withDelta:0.01];
[[expectFutureValue(theValue([ratingService lastResult])) shouldEventuallyBeforeTimingOutAfter(3)] beNonNil];
});
ASRatingCalculator 和 ASRatingService 两个类都实现了inputScores:方法，ASRatingService直接使用了ASRatingCalculator计算出来的平均值，例子比较简单。
① 为ASRatingCalculator建立一个mock虚拟对象；
② 把ratingService的calcultor方法实现替换掉，方法返回我们创建的mock对象；
③ 捕获mock inputScore:方法的第一个参数，确认该方法后续是否被调用；
④ ratingService 调用自己的inputScores:；
⑤ 此时捕获的参数应该不为空，证明mock也响应了inputScores:；
⑥ 把mock 的求平均数方法替换掉，直接返回我们期望中的值；
⑦ 测试ratingService的平均值是否正确；
⑧ 保证mock能响应removeMaxAndMin消息；
stub: 可以替换真实对象以及构造mock对象的方法实现，不用关注方法内部逻辑，保证输入输出是正确的；
假如mock对象运行期收到了不能识别的消息，请添加任意stub该方法，因为该对象并不能响应所mock类的所有消息，只会对你标记的selector做处理, 如stub,captureArgument:等。所以，在测试过程中，可以对依赖的类的实例会收到的消息全部做stub处理。
一些吐槽
kiwi在易用性上是高于于XCTest的，其测试用例在运行期插入了很多XCTest方法，但在未完全执行所有测试用例时，是无法看到单个测试方法的，更无法执行单个测试。kiwi的最小测试单位为一个测试用例类，而XCTest的最小测试单位为测试用例类的一个测试方法。
谢谢观看，水平有限，欢迎指出错误
参考资料
https://github.com/kiwi-bdd/Kiwi
https://github.com/allending/Kiwi/wiki/Expectations
https://onevcat.com/2014/02/ios-test-with-kiwi/
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