no-standalone-expect.md

Disallow using expect outside of it or test blocks (no-standalone-expect)

💼 This rule is enabled in the ✅ recommended config.

Prevents expect statements outside of a test or it block. An expect within a helper function (but outside of a test or it block) will not trigger this rule.

Rule details

This rule aims to eliminate expect statements that will not be executed. An expect inside of a describe block but outside of a test or it block or outside a describe will not execute and therefore will trigger this rule. It is viable, however, to have an expect in a helper function that is called from within a test or it block so expect statements in a function will not trigger this rule.

Statements like expect.hasAssertions() will NOT trigger this rule since these calls will execute if they are not in a test block.

Examples of incorrect code for this rule:

// in describe
describe('a test', () => {
  expect(1).toBe(1);
});

// below other tests
describe('a test', () => {
  it('an it', () => {
    expect(1).toBe(1);
  });

  expect(1).toBe(1);
});

Examples of correct code for this rule:

// in it block
describe('a test', () => {
  it('an it', () => {
    expect(1).toBe(1);
  });
});

// in helper function
describe('a test', () => {
  const helper = () => {
    expect(1).toBe(1);
  };

  it('an it', () => {
    helper();
  });
});

describe('a test', () => {
  expect.hasAssertions(1);
});

*Note that this rule will not trigger if the helper function is never used even though the expect will not execute. Rely on a rule like no-unused-vars for this case.

Options

additionalTestBlockFunctions

This array can be used to specify the names of functions that should also be treated as test blocks:

{
  "rules": {
    "jest/no-standalone-expect": [
      "error",
      { "additionalTestBlockFunctions": ["each.test"] }
    ]
  }
}

The following is correct when using the above configuration:

each([
  [1, 1, 2],
  [1, 2, 3],
  [2, 1, 3],
]).test('returns the result of adding %d to %d', (a, b, expected) => {
  expect(a + b).toBe(expected);
});

When Not To Use It

Don't use this rule on non-jest test files.