Update functional test documentation

[AaronFeickert]

Description

Updates the functional test documentation to fix issues and improve readability.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature/Enhancement (non-breaking change which adds functionality or enhances an existing one)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactor
• New or updated tests
• Dependency Update

Notes to Reviewers

These directions were tested on a macOS 15.1.1 installation.

Checklist

• I have performed a self-review of my code.
• I have commented my code where necessary.
• I have updated the documentation if needed.
• My changes do not introduce new warnings.
• I have added tests that prove my changes are effective or that my feature works.
• New and existing tests pass with my changes.

Related Issues

None.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.43%. Comparing base (b5f84a0) to head (bc73b2f).
Report is 2 commits behind head on main.

@@            Coverage Diff             @@
##             main     #529      +/-   ##
==========================================
- Coverage   58.55%   58.43%   -0.13%     
==========================================
  Files         277      277              
  Lines       29341    29341              
==========================================
- Hits        17182    17145      -37     
- Misses      12159    12196      +37     

see 5 files with indirect coverage changes

[storopoli]

Minor formatting nits and one clarification on --no-root.

[storopoli]

ACK bc73b2f