writing-testslisted

# Writing Tests cc-port tests use `testutil.SetupFixture(t)` against `testdata/dotclaude/`. testify `require` for preconditions, `assert` for behavioral claims after the act. Table-driven via `t.Run`. ## Workflow ```dot digraph test_workflow { entry [shape=doublecircle, label="About to write\nor edit a test"]; behavior [shape=box, label="Identify the\nsingle behavior"]; observable [shape=diamond, label="Observable on the\nexported API?"]; seamable [shape=diamond, label="Production code wants\nthe seam regardless?"]; introduce_seam [shape=box, label="Introduce seam in\nproduction code first"]; reframe [shape=octagon, style=filled, fillcolor=red, label="Reframe at exported\nsurface or delete"]; arrange [shape=box, label="Source the\narrange data"]; body [shape=box, label="Structure the body\n(AAA or table row)"]; independence [shape=box, label="Guard\nindependence"]; gate [shape=box, label="Final quality gate"]; pass [shape=diamond, label="All checks\npass?"]; done [shape=doublecircle, label="Done"]; entry -> behavior; behavior -> observable; observable -> arrange [label="yes"]; observable -> seamable [label="no"]; seamable -> introduce_seam [label="yes"]; seamable -> reframe [label="no"]; introduce_seam -> arrange; reframe -> behavior; arrange -> body; body -> independence; independence -> gate; gate -> pass; pass -> done [label="yes"]; pass -> behavior [label="no"]; } `