Winston Jodjana authored Jan 04, 2022 and @thx committed Jan 04, 2022

Tests renamed and cleaned

Provide a couple of ArrayStack tests

Fix compilation warnings

Do minor copyediting

Document assertEquals

Enboxen the section comments

@thx authored Oct 03, 2021 and @thx committed Jan 04, 2022

In JUnit 5, the @Before keyword used in JUnit4 is deprecated. This means
that the @Before-annotated methods in the source tree currently are
simply no-op. Using its replacement @BeforeEach fixes this.

Thanks to @tenzinhl for discovering this fix!