assertEquals(Double, Double) 和 assertEquals(double, double, delta) 之间的 Junit 区别 [英] Junit difference between assertEquals(Double, Double) and assertEquals(double, double, delta)

问题描述

我有一个 junit 测试断言两个 Double 对象如下:

I had a junit test asserting two Double objects with the following:

Assert.assertEquals(Double expected, Double result);

这很好，然后我决定将其更改为使用原始 double 代替，结果证明已弃用，除非您还提供增量.

This was was fine then I decided to change it to use the primitive double instead which turned out to be deprecated unless you also provide a delta.

所以我想知道在这个 assertEquals 中使用 Double 对象或原始类型有什么区别?为什么使用没有 delta 的对象可以，但不推荐使用没有 delta 的原语?Java 是否在后台做了一些已经考虑了默认增量值的事情?

so what I am wondering is what is the difference between using the Double object or the primitive type in this assertEquals? Why is using the objects without a delta ok but then using the primitives without a delta is deprecated? Is Java doing something in the background which already has a default delta value taken into account?

谢谢.

推荐答案

没有 在 JUnit 中使用签名声明方法

assertEquals(Double expected, Double result);

然而，有一个对象是通用的:

There is one, however, generic for objects:

assertEquals(Object expected, Object result);

这会调用对象的 equals 方法，正如您所料，不建议使用它来比较 Double 对象.

This calls the objects' equals method and as you can expect, it is not recommended to use this for comparing Double objects.

对于双打，正如您所观察到的，绝对有必要使用增量进行比较，以避免浮点舍入问题(已在其他一些答案中进行了解释).如果您使用带有 double 参数

For doubles, as you observed, it is absolutely necessary to use a delta for comparison, to avoid issues with floating-point rounding (explained already in some other answers). If you use the 3-argument version of assertEquals with double arguments

assertEquals(double expected, double actual, double delta);

您的 Double 将被静默地拆箱为 double 并且一切正常(并且您的测试不会意外失败 :-).

your Doubles will get silently unboxed to double and everything will work fine (and your tests won't fail unexpectedly :-).

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