valid-expect.md

Enforce valid expect() usage (valid-expect)

Ensure expect() is called with a single argument and there is an actual expectation made.

Rule details

This rule triggers a warning if expect() is called with more than one argument or without arguments. It would also issue a warning if there is nothing called on expect(), e.g.:

expect();
expect('something');

or when a matcher function was not called, e.g.:

expect(true).toBeDefined;

or when an async assertion was not awaited or returned, e.g.:

expect(Promise.resolve('Hi!')).resolves.toBe('Hi!');

This rule is enabled by default.

Options

{
  type: 'object',
  properties: {
    alwaysAwait: {
      type: 'boolean',
      default: false,
    },
  },
  additionalProperties: false,
}

alwaysAwait

Enforces to use await inside block statements. Using return will trigger a warning. Returning one line statements with arrow functions is always allowed.

Examples of incorrect code for the { "alwaysAwait": true } option:

// alwaysAwait: true
test('test1', async () => {
  await expect(Promise.resolve(2)).resolves.toBeDefined();
  return expect(Promise.resolve(1)).resolves.toBe(1); // `return` statement will trigger a warning
});

Examples of correct code for the { "alwaysAwait": true } option:

// alwaysAwait: true
test('test1', async () => {
  await expect(Promise.resolve(2)).resolves.toBeDefined();
  await expect(Promise.resolve(1)).resolves.toBe(1);
});

test('test2', () => expect(Promise.resolve(2)).resolves.toBe(2));

Default configuration

The following patterns are considered warnings:

expect();
expect().toEqual('something');
expect('something', 'else');
expect('something');
expect(true).toBeDefined;
expect(Promise.resolve('hello')).resolves;
expect(Promise.resolve('hello')).resolves.toEqual('hello');
Promise.resolve(expect(Promise.resolve('hello')).resolves.toEqual('hello'));
Promise.all([
  expect(Promise.resolve('hello')).resolves.toEqual('hello'),
  expect(Promise.resolve('hi')).resolves.toEqual('hi'),
]);

The following patterns are not warnings:

expect('something').toEqual('something');
expect([1, 2, 3]).toEqual([1, 2, 3]);
expect(true).toBeDefined();
await expect(Promise.resolve('hello')).resolves.toEqual('hello');
await Promise.resolve(
  expect(Promise.resolve('hello')).resolves.toEqual('hello'),
);
await Promise.all(
  expect(Promise.resolve('hello')).resolves.toEqual('hello'),
  expect(Promise.resolve('hi')).resolves.toEqual('hi'),
);