refactor(test): port testing doubles to an independent module

[hasundue]

• build(deps): update dependencies
• test: add createCommandStub
• test: add assertSomeSpyCall()
• test: add stubs for filesystem

[codecov]

Codecov Report

Attention: 22 lines in your changes are missing coverage. Please review.

Comparison is base (404b44c) 82.99% compared to head (08d4de7) 82.29%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #62      +/-   ##
==========================================
- Coverage   82.99%   82.29%   -0.71%     
==========================================
  Files          16       17       +1     
  Lines         588      689     +101     
  Branches       86       91       +5     
==========================================
+ Hits          488      567      +79     
- Misses        100      122      +22     

Files	Coverage Δ
lib/std/assert.ts	100.00% <100.00%> (ø)
lib/std/testing.ts	100.00% <100.00%> (ø)
lib/testing.ts	76.59% <76.59%> (ø)

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