prefer-expect-assertions.md

vitest/prefer-expect-assertions

📝 Enforce using expect assertions instead of callbacks.

⚠️ This rule warns in the 🌐 all config.

💡 This rule is manually fixable by editor suggestions.

Ensure every test to have either expect.assertions(<number of assertions>) OR expect.hasAssertions() as its first expression.

This will warn if a test has no assertions, or if it has assertions but they are not the first expression.

Examples

Examples of incorrect code for this rule:

test('no assertions', () => {
  // ...
})

test('assertions not first', () => {
  expect(true).toBe(true)
  // ...
})

Examples of correct code for this rule:

test('assertions first', () => {
  expect.assertions(1)
  // ...
})

test('assertions first', () => {
  expect.hasAssertions()
  // ...
})

Options

Name	Description	Type
disallowHasAssertions	Warn when expect.hasAssertions() is used instead of expect.assertions().	Boolean
onlyFunctionsWithAsyncKeyword	Only check test functions declared with the async keyword.	Boolean
onlyFunctionsWithExpectInCallback	Only check test functions that contain expect in callbacks.	Boolean
onlyFunctionsWithExpectInLoop	Only check test functions that contain expect inside loops.	Boolean

onlyFunctionsWithAsyncKeyword (default: false)

When true, only functions with the async keyword will be checked.

when this option is enabled the following code will be considered incorrect:

test('assertions first', async () => {
  const data = await fetchData()
  expect(data).toBe('peanut butter')
})

To fix this, you'll need to add expect.assertions(1) or expect.hasAssertions() as the first expression:

test('assertions first', async () => {
  expect.assertions(1)
  const data = await fetchData()
  expect(data).toBe('peanut butter')
})

onlyFunctionsWithExpectInLoop (default: false)

When true, only functions with expect in a loop will be checked.

when this option is enabled the following code will be considered incorrect:

test('assertions first', () => {
  for (let i = 0; i < 10; i++) {
    expect(i).toBeLessThan(10)
  }
})

To fix this, you'll need to add expect.assertions(1) or expect.hasAssertions() as the first expression:

test('assertions first', () => {
  expect.hasAssertions()
  for (let i = 0; i < 10; i++) {
    expect(i).toBeLessThan(10)
  }
})

onlyFunctionsWithExpectInCallback

When true, only functions with expect in a callback will be checked.

when this option is enabled the following code will be considered incorrect:

test('assertions first', () => {
  fetchData((data) => {
    expect(data).toBe('peanut butter')
  })
})

To fix this, you'll need to add expect.assertions(1) or expect.hasAssertions() as the first expression:

test('assertions first', () => {
  expect.assertions(1)
  fetchData((data) => {
    expect(data).toBe('peanut butter')
  })
})

disallowHasAssertions (default: false)

When true, expect.hasAssertions() will be reported in favor of expect.assertions(). Suggestions for missing assertions will only include expect.assertions().

when this option is enabled the following code will be considered incorrect:

test('has assertions', () => {
  expect.hasAssertions()
  expect(value).toBe(1)
})

To fix this, use expect.assertions(<number of assertions>) instead:

test('has assertions', () => {
  expect.assertions(1)
  expect(value).toBe(1)
})