[Task]: Decompose and clean up test suites

[rian-be]

Summary

Clean up and decompose the test suites across Mutator packages so scenarios stay focused, setup becomes reusable, and future platform work does not accumulate in oversized test fixtures.

Goal

Improve test maintainability by splitting broad fixtures into package-focused concerns, extracting stable shared test support where appropriate, and normalizing naming and scenario boundaries.

Problem

Several test projects are starting to accumulate mixed concerns in large files or repeated local setup. As governance, runtime, and Redis coverage expand, broad fixtures become harder to read, harder to extend safely, and harder to review.

Scope

• Split oversized test fixtures into focused package level concerns
• Extract shared test support where repetition is real and stable
• Normalize naming so test files and fixture classes reflect the scenario they cover
• Reduce mixed concerns inside single files where execution, resolution, approval, or provider behavior are bundled together
• Track package specific cleanup through dedicated child issues

Design Expectations

• Test cleanup should preserve behavior while improving readability and extension points.
• Shared helpers should be extracted only when they remove real duplication rather than hiding test intent.
• Package boundaries should remain visible in the test layout.
• Refactoring should keep scenarios easy to scan and debug.

Acceptance Criteria

• Each affected test package has dedicated cleanup issue with concrete scope
• Oversized or mixed concern fixtures are decomposed into focused files or fixtures
• Shared setup is extracted only where justified by repeated usage
• Naming across cleaned up test areas is more consistent and scenario oriented

Non-Goals

• This issue does not change runtime behavior or public APIs by itself
• This issue does not force every test helper into one global shared library
• This issue does not rewrite unrelated assertions only for style consistency

Notes

This is an umbrella task. Execution should happen through package focused cleanup issues.