copyedit gui->testing

[Tom-Willemsen]

Copyedit GUI -> Testing section. Summary of changes below.

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Adding unit tests

• General sentence-level/formatting changes

An introduction to unit testing

• General sentence-level/formatting changes
• Run through all examples to check they still work, update where they didn't
• Update instructions and screenshots for newer versions of Eclipse

Mockito

• Run through examples to check they work, update where they didn't
• Corrections/updates for newer Mockito APIs
  • e.g. recommend @Mock over Mockito.mock() as it's type-safe with generics
• Link much more prominently to authoritative upstream documentation
  • I'm not actually sure we really want to keep much of this page - it's mostly a duplicate of the (higher-quality) upstream documentation. But have kept for now as it's "only" a few hundred lines of duplication.

Squish

• General formatting improvements
• Correct various dead links

Squish BDD tools

• General formatting improvements

Test naming

• General sentence-level/formatting changes
• No substantive change to the documented conventions
• Correct misleading example