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vitest/prefer-expect-type-of Style

🛠️ An auto-fix is available for this rule.

What it does

Enforce using expectTypeOf instead of expect(typeof ...)

Why is this bad?

Vitest provide a more expressive type-safe way to test type than using expect(typeof ...)

Examples

Examples of incorrect code for this rule:

test('type checking', () => {
  expect(typeof 'hello').toBe('string')
  expect(typeof 42).toBe('number')
  expect(typeof true).toBe('boolean')
  expect(typeof {}).toBe('object')
  expect(typeof () => {}).toBe('function')
  expect(typeof Symbol()).toBe('symbol')
  expect(typeof 123n).toBe('bigint')
  expect(typeof undefined).toBe('undefined')
})

Examples of correct code for this rule:

test("type checking", () => {
  expectTypeOf("hello").toBeString();
  expectTypeOf(42).toBeNumber();
  expectTypeOf(true).toBeBoolean();
  expectTypeOf({}).toBeObject();
  expectTypeOf(() => {}).toBeFunction();
  expectTypeOf(Symbol()).toBeSymbol();
  expectTypeOf(123n).toBeBigInt();
  expectTypeOf(undefined).toBeUndefined();
});

How to use

To enable this rule using the config file or in the CLI, you can use:

Config (.oxlintrc.json)

{
  "plugins": ["vitest"],
  "rules": {
    "vitest/prefer-expect-type-of": "error"
  }
}

CLI

oxlint --deny vitest/prefer-expect-type-of --vitest-plugin

References

• Rule Source