valid-expect.md

Enforce valid expect() usage (vitest/valid-expect)

💼 This rule is enabled in the ✅ recommended config.

⚠️ This rule warns in the 🌐 all config.

🔧 This rule is automatically fixable by the --fix CLI option.

This rule triggers a warning if expect is called with no argument or with more than one argument. You change that behavior by setting the minArgs and maxArgs options.

Options

1. alwaysAwait

• Type: boolean

• Default: false

• Enforce expect to be called with an await expression.

  // ✅ good
  await expect(Promise.resolve(1)).resolves.toBe(1)
  await expect(Promise.reject(1)).rejects.toBe(1)
  
  // ❌ bad
  expect(Promise.resolve(1)).resolves.toBe(1)
  expect(Promise.reject(1)).rejects.toBe(1)

2. asyncMatchers

• Type: string[]
• Default: []

{
  "vitest/valid-expect": ["error", {
    "asyncMatchers": ["toBeResolved", "toBeRejected"]
  }]
}

avoid using asyncMatchers with expect:

3. minArgs

• Type: number

• Default: 1

• Enforce expect to be called with at least minArgs arguments.

  // ✅ good
  expect(1).toBe(1)
  expect(1, 2).toBe(1)
  expect(1, 2, 3).toBe(1)
  
  // ❌ bad
  expect().toBe(1)
  expect(1).toBe()

4. maxArgs

• Type: number

• Default: 1

• Enforce expect to be called with at most maxArgs arguments.

• Exception: expect(value, "message") is allowed.

  // ✅ good
  expect(1).toBe(1)
  expect(1, "expect value to be one").toBe(1)
  const message = "expect value to be one"
  expect(1, `Error Message: ${message}`).toBe(1)
  
  
  // ❌ bad
  expect(1, 2, 3, 4).toBe(1)