Add unit test coverage for Knative plugin utility helpers

[intojhanurag]

Add unit test coverage for shared Knative plugin utilities (getAge and isNullable) to prevent regressions in time formatting and nullable field handling. Tests are deterministic and cover key edge cases without changing existing behavior.

[achalcipher]

I’ve just wrapped up a comprehensive testing overhaul for our shared Knative plugin utilities—specifically getAge and isNullable.

While these functions seem simple on the surface, they are the "glue" in our UI. Any regression here ripples across the entire plugin. I wanted to move beyond basic "happy path" testing and ensure these utilities are bulletproof, especially regarding weird edge cases we might encounter in production.

Why this matters:
Zero Flakiness: By mocking Date.now(), I’ve ensured that getAge tests won't fail based on when or where the CI/CD pipeline runs.

Type Safety: The isNullable tests now explicitly validate TypeScript type-guard assertions. This means fewer undefined errors in our downstream components.

Predictable UI: We now have documented and tested behavior for how the UI handles "future" timestamps or malformed ISO strings, preventing weird "NaN" or "undefined" labels from appearing to users.

🔍 What’s in the Box?

1. getAge Utility (20 Test Cases) I focused heavily on boundary transitions. For example, I verified exactly when "59 minutes" clicks over to "1 hour" and how we handle multi-day durations.

Key Additions: Handled sub-second precision, malformed strings, and varied ISO formats to ensure our time-formatting is resilient to different backend responses.

2. isNullable Utility (28 Test Cases) The goal here was distinction. It’s easy to catch null, but harder to ensure you aren't accidentally catching 0, false, or an empty string.

Key Additions: Tested against Symbols, RegEx, and complex class instances to ensure our type-guarding logic is surgical.

🛠 Infrastructure Improvements
I added a vitest.config.ts. This standardizes our test environment, making it easier for others to jump in and add tests without worrying about configuration drift.