test: reference functions directly

[merceyz]

What's the problem this PR addresses?

Some of our test code is referencing methods in the same file through exports which works due to how Babel transpiles the files, however when transpiled by esbuild it throws.

TypeScript doesn't complain because @types/node contains declare var exports: any.

How did you fix it?

Reference the functions directly.

Checklist

• I have read the Contributing Guide.
• I have set the packages that need to be released for my changes to be effective.
• I will check that all automated PR checks pass before the PR gets reviewed.