add test case for hashcode in attribute

[danglotb]

Hello,

I propose this changes to specify the hashCode of the object org.jsoup.nodes.Attribute.

[cketti]

Why? The return value of hashCode() is typically an implementation detail, not part of the public API.

[danglotb]

The return value of hashCode() is typically an implementation detail, not part of the public API.

I totally agree with you.

But I think the hashCode() method worth a test case since it has to be deterministic.

[cketti]

Test the contract then. The documentation is very explicit on what that includes: https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#hashCode--

You might find this helpful: http://jqno.nl/equalsverifier/

[jhy]

Thanks. I agree with @cketti, this does not test the functionality or the contract, and the impl is trivial anyway.