8. In-source testing

src/add.ts

export function add(a: number, b: number) { return a + b }

if (import.meta.vitest) {
  const { it, expect } = import.meta.vitest
  it('add', () => {
    expect(add(1, 1)).toBe(2)
  })
}

• Gated entirely by the if (import.meta.vitest) guard; test/it/expect/etc. are pulled off import.meta.vitest itself (an injected object), not from a 'vitest' import specifier, the extractor’s “how did this binding get here” resolution needs a special case: a MemberExpression destructure off import.meta.vitest is a Vitest-global-equivalent binding, regardless of the file’s globals setting.
• Governed by includeSource config: string[] glob list, resolved relative to root, default [] (feature is opt-in, off unless a project lists source globs, e.g. includeSource: ['src/**/*.{js,ts}']). A file only contributes in-source tests if it matches includeSource (in addition to actually containing import.meta.vitest blocks). Note this is independent of, and additive to, the regular include test-file glob, a file can be scanned for in-source tests without matching include at all, since it’s not a “test file” in the ordinary sense (it’s application source with embedded tests).
• Production exclusion is a build-time concern (Vite define: { 'import.meta.vitest': 'undefined' } enabling dead-code elimination), irrelevant to the static extractor except as confirmation that import.meta.vitest guards are the sole and idiomatic gate; the extractor doesn’t need to model bundler DCE, just recognize the guard shape.

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