如何测试实现 NSCoding 的简单数据对象类？

Question

我有一个需要序列化和反序列化的小数据对象。假设它被称为WeatherDetails，它看起来像这样：

WeatherDetails.h

@interface WeatherDetails : NSObject <NSCoding>
{
@private

@protected
}

#pragma mark - Properties

@property (nonatomic, copy) NSString *weatherCode;
@property (nonatomic, copy) NSString *weatherDescription;

@end

WeatherDetails.m

#import "WeatherDetails.h"

@implementation WeatherDetails

NSString *const WEATHER_DETAILS_WEATHER_CODE_KEY = @"s";
NSString *const WEATHER_DETAILS_WEATHER_DESCRIPTION_KEY = @"sT";

#pragma mark - Initialization, NSCoding and Dealloc

- (instancetype)initWithCoder:(NSCoder *)aDecoder
{
    self = [super init];

    _weatherCode = [aDecoder decodeObjectForKey:@"weatherCode"];
    _weatherDescription = [aDecoder decodeObjectForKey:@"weatherDescription"];

    return self;
}

- (void)encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeObject:_weatherCode forKey:@"weatherCode"];
    [aCoder encodeObject:_weatherDescription forKey:@"weatherDescription"];
}

目前我的测试是这样的；

#import <XCTest/XCTest.h>
#import <OCMock/OCMock.h>
#import "WeatherDetails.h"
@interface WeatherDetailsTests : XCTestCase

@end

@implementation WeatherDetailsTests

- (void)testThatWeatherCodeIsEncoded
{
    WeatherDetails *details = [[WeatherDetails alloc] init];
    [details setWeatherCode:@"A"];

    NSData *archive = [NSKeyedArchiver archivedDataWithRootObject:details];

    WeatherDetails *unarchive = [NSKeyedUnarchiver unarchiveObjectWithData:archive];

    XCTAssertEqualObjects(@"A", [unarchive weatherCode]);
}

- (void)testThatWeatherDescriptionIsEncoded
{
    WeatherDetails *details = [[WeatherDetails alloc] init];
    [details setWeatherDescription:@"A"];

    NSData *archive = [NSKeyedArchiver archivedDataWithRootObject:details];

    WeatherDetails *unarchive = [NSKeyedUnarchiver unarchiveObjectWithData:archive];

    XCTAssertEqualObjects(@"A", [unarchive weatherDescription]);
}

我有一种直觉，这种测试所有属性是否正确编码的方法并不是真正的最佳方法，因为存在重复，但我真的想不出更好的方法。有没有人对我有改进的建议？

Answer 1

您真正要测试的是对象在归档之前和之后是否相同。

在您的WeatherDetails 中实现一个方法来比较对象（或覆盖isEqual:）。

- (BOOL)isEqualToWeatherDetails:(WeatherDetails *)details
{
    if (![details isKindOfClass:[WeatherDetails class]]) return NO;
    return [self.weatherCode == details.weatherCode && self.weatherDescription isEqualToString:details.weatherDescription];
}

然后你可以一次完成所有的相等比较：

- (void)testNSCoder
{
    WeatherDetails *details = [[WeatherDetails alloc] init];
    [details setWeatherCode:@"A"];
    details.weatherDescription = @"Cloudy";

    NSData *archive = [NSKeyedArchiver archivedDataWithRootObject:details];

    WeatherDetails *unarchive = [NSKeyedUnarchiver unarchiveObjectWithData:archive];

    XCTAssertTrue([details isEqualToWeatherDetails:unarchive]);
}

如果您覆盖isEqual:，那么您可以比较这样做：

XCTAssertEqualObjects(details, unarchive);

Apple 倾向于添加其他方法（isEqualToArray:、isEqualToDictionary:）。 isEqual: 被 NSSet 和 NSDictionary 等集合使用

Answer 2

最后我通过应用custom assertion 对其进行了改进；

什么时候使用它

只要满足以下任一条件，我们就应该考虑创建自定义断言：

• 我们发现自己在一个又一个的测试中编写（或克隆）相同的断言逻辑
• 我们发现自己在测试的结果验证部分编写条件测试逻辑。也就是说，我们对断言方法的调用嵌入在 if 语句或循环中。
• 我们测试的结果验证部分受到模糊测试的影响，因为我们在测试中使用程序性而非声明性结果验证。
• 每当断言失败时，我们都会进行频繁调试，因为它们没有提供足够的信息。

自定义断言目前如下所示：

/*!
 * @define XCTAssertEqualSerialized(value, object, selector)
 * Serializes (\a object), then desirializes it and compares result's property (\a propertyName) to (\a value) with XCTAssertEqualObjects
 * @param value Value to compare.
 * @param object Object to serialize.
 * @param selector Objects property to compare.
 */

#define XCTAssertEqualSerialized(value, object, selector) \
({ \
NSData *archived = [NSKeyedArchiver archivedDataWithRootObject:object]; \
NSObject *unarchived = [NSKeyedUnarchiver unarchiveObjectWithData:archived]; \
XCTAssertEqualObjects(value, [unarchived valueForKeyPath:NSStringFromSelector(selector)]); \
})

/*!
 * @define XCTAssertNotNilSerialized(object, selector)
 * Serializes (\a object), then desirializes it and checks result's property (\a propertyName) is not nil with XCTAssertNotNil
 * @param object Object to serialize.
 * @param selector Objects property to compare.
 */

#define XCTAssertNotNilSerialized(object, selector) \
({ \
NSData *archived = [NSKeyedArchiver archivedDataWithRootObject:object]; \
NSObject *unarchived = [NSKeyedUnarchiver unarchiveObjectWithData:archived]; \
XCTAssertNotNil([unarchived valueForKeyPath:NSStringFromSelector(selector)]); \
})

测试结果如下：

- (void)testThatWeatherCodeIsEncoded
{
    WeatherDetails *details = [[WeatherDetails alloc] init];
    [details setWeatherCode:@"A"];

    XCTAssertEqualSerialized(@"A", details, @selector(weatherCode));
}

- (void)testThatWeatherDescriptionIsEncoded
{
    WeatherDetails *details = [[WeatherDetails alloc] init];
    [details setWeatherDescription:@"A"];

    XCTAssertEqualSerialized(@"A", details, @selector(weatherDescription));
}