Junit difference between assertEquals(Double, Double) and assertEquals(double, double, delta)

Question

I had a junit test asserting two Double objects with the following: ``` Assert.assertEquals(Double expected, Double result); ``` 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. 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? Thanks.

Accepted Answer

There is NO assert method in JUnit with the signature

```
assertEquals(Double expected, Double result);
```

There is one, however, generic for objects:

```
assertEquals(Object expected, Object result);
```

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

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);
```

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

Junit difference between assertEquals(Double, Double) and assertEquals(double, double, delta)

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