#require-local-test-context-for-concurrent-snapshots

#Configuration

import { defineConfig, rstestPlugin } from '@rslint/core';

export default defineConfig([
  rstestPlugin.configs.recommended,
  {
    rules: {
      'rstest/require-local-test-context-for-concurrent-snapshots': 'error',
    },
  },
]);

#Rule Details

Concurrent Rstest tests must use the expect provided by their local Test Context for snapshot assertions. A global or imported expect can share snapshot state between concurrently running tests.

Examples of incorrect code for this rule:

test.concurrent('renders', () => {
  expect(render()).toMatchSnapshot();
});

Examples of correct code for this rule:

test.concurrent('renders', ({ expect }) => {
  expect(render()).toMatchSnapshot();
});

An explicit inner sequential or concurrent registration overrides the mode inherited from an enclosing describe block. The mode is read only from the chained modifiers: Rstest takes just timeout, retry, repeats and meta out of the options object of a (name, options, fn) registration, so concurrent and sequential written there have no effect at runtime and none here either.

The rule recognizes Rstest aliases, named callbacks, .each, .for, import.meta.rstest, and @rstest/playwright registrations.

Assertions written inside a closure, hook or helper declared within a concurrent body are checked too, because such a function runs as part of the concurrent test whenever it runs at all:

test.concurrent('renders', async () => {
  await Promise.all(items.map(async item => {
    expect(item).toMatchSnapshot();
  }));
});

A helper declared outside every registration callback is not checked, since the rule cannot tell which tests call it. A callback passed by a name the type checker cannot resolve is only matched against a function declared at the top level of the file under that exact name, so a same-named function nested inside another callback is never blamed for a test that does not run it.

Rstest's matchSnapshot Chai alias is also checked because it uses the same snapshot state as toMatchSnapshot. A Chai chain may carry several assertions, so every matcher in the chain is considered and expect(value).to.be.a('string').and.matchSnapshot() is reported once.