Update tests

[hoangtrvu]

:v:

/cc @zendesk/vegemite

Description

This PR is mainly for improving our current tests. Other than that, it also remove some unused variables.

Tasks

• [x] Remove unused variables
• [x] Add additional test cases
• [x] Make tests self-contained and independent from fixtures
• [x] Fix tests that always pass
• [x] Fix tests that might pass/fail depending on their execution order

Risks

• [LOW] Only remove unused code and update test files

[hoangtrvu]

PR updated based on @svizzari's comments

[svizzari]

PR updated based on @svizzari's comments

Great, thanks @hoangtrvu. My 👍 stands