cocoa - STAssertEquals NSTimeIntervals

Question

我正在为我的 cocoa 类编写单元测试用例。下面是测试用例。我无法弄清楚为什么这个测试用例失败，即使断言消息中的 expect 和 diff 是相同的。我怀疑这可能与 double 或 NSTimeInterval 的计算方式有关


NSTimeInterval 天 = 60*60*24;

NSDate * 当前 = [NSDate 日期];

NSDate * daysAgo = [NSDate dateWithTimeInterval:-6*天sinceDate:当前];

NSTimeInterval diff = [当前时间IntervalSinceDate:daysAgo];

NSTimeInterval 期望 = 6 * 天；

STAssertEquals(expect, diff, @"期望失败:%ld，获取 %ld", Expect, diff);

Answer 1

您正在比较 NSTimeIntervals，其类型定义为 double。阅读例如http://floating-point-gui.de/ (或 http://download.oracle.com/docs/cd/E19957-01/806-3568/ncg_goldberg.html )以找出为什么不能对浮点/ double 计算使用精确比较。您应该始终比较间隔，例如通过使用

STAssertEqualsWithAccuracy(expect, diff, 0.001, @"期望失败:%ld，获取 %ld", Expect, diff);