require-test-output.md

Enforce use of output assertions in rule tests (require-test-output)

When writing tests for a fixable rule with RuleTester, you can assert the autofix output of your test cases.

As of ESLint 7, test cases that trigger an autofix are required to provide the output property.

However, it can be easy to forget to assert the output of a particular test case, leading to the autofix being untested. And even tests that do not trigger an autofix can benefit from asserting that they have no autofix using output: null.

Rule Details

This rule ensures all invalid test cases have output assertions.

Examples of incorrect code for this rule:

/* eslint eslint-plugin/require-test-output: error */

new RuleTester().run('example-rule', rule, {
  valid: [],
  invalid: [
    {
      code: 'foo',
      output: 'bar',
      errors: ['baz'],
    },
    {
      code: 'bar',
      errors: ['baz'],
    },
  ],
});

Examples of correct code for this rule:

/* eslint eslint-plugin/require-test-output: error */

new RuleTester().run('example-rule', rule, {
  valid: [],
  invalid: [
    {
      code: 'foo',
      output: 'bar',
      errors: ['baz'],
    },
    {
      code: 'bar',
      output: 'qux',
      errors: ['baz'],
    },
    {
      code: 'foo',
      output: null, // asserts that there is no autofix
      errors: ['baz'],
    },
  ],
});

Options

This rule takes an optional object containing:

• boolean -- consistent -- only require output assertions when some test cases have them (default false)

Further Reading

• RuleTester documentation