test-runner-segregation

Bun-side and foreign-side test runners are never mixed within a package.

Runs under: @noctcore/harness lint-meta, not ESLint · Factory: createTestRunnerSegregationRule from @noctcore/lint-meta-rules · Category: testing · Fails CI by default: yes

Why

A package that mixes two test runners (e.g. bun:test and Vitest) has tests that run under one command but not another — a coverage gap hiding in plain sight. Segregating the runner by workspace, and enforcing it per test file, keeps every test attributable to exactly one runner.

What it flags

Directories split into a bun set (from bunPackageGlobs minus vitestDirs, plus bunExtraDirs) and the foreign set (vitestDirs). For every *.test.ts(x) file:

• bun-side — must import the bun runner (bunRunnerImport) and must NOT import the foreign runner (foreignRunnerImport);
• foreign-side — must NOT import the bun runner.

What it does not flag

• A foreign-side test with no direct foreign-runner import: the runner may arrive transitively via shared test-utils.
• A bun-side test that imports bunRunnerImport and not the foreign runner.
• Anything in a vitestDirs directory for a missing bun import (those dirs leave the bun set).
• Files that are not *.test.ts / *.test.tsx (setup files, helpers), and require() or dynamic imports: only a from '<runner>' import is read.

Options

createTestRunnerSegregationRule(options?: TestRunnerSegregationOptions): IMetaRule

Option	Type	Default	Meaning
bunPackageGlobs	string[]	['packages/*/package.json']	Packages whose dirs default to the bun runner.
bunExtraDirs	string[]	[]	Extra bun-runner directories.
vitestDirs	string[]	[]	Directories that use the foreign (non-bun) runner.
bunRunnerImport	string	'bun:test'	The bun-side runner import specifier.
foreignRunnerImport	string	'vitest'	The foreign runner import specifier.
ciCritical	boolean	true	Whether a violation fails CI.

When not to use it

If your repo uses a single test runner everywhere, this rule has nothing to segregate.