`.calledWithContaining(...)`

[wh1t3cAt1k]

That would expect a Partial of each of the arguments and apply expect.objectContaining matcher internally to each of the passed arguments.

How it is useful

Imagine method A receiving an object { x: number, y: number, z: number } as a parameter and delegating to method B which wants an {x: number, y: number }. To avoid extra memory allocations (our app is sensitive to that), we pass the object as-is since it satisfies the reduced shape expected by method B.

However, .calledWith fails because there is an extra unexpected property.

Workaround:

• We can currently emulate this by passing the expect.objectContaining matcher inside, but it has no type safety with Typescript.
• Alternatively, we do an extra object allocation by destructuring the argument and reassembling only { x, y } for method B.

[timkindberg]

You can also achieve this using the allArgs helper.

Maybe something like this:

const fn = jest.fn()
const objectContaining = (obj) => when.allArgs((args, equals) => equals(args[0], expect.objectContaining(obj)))

when(fn)
  .calledWith(objectContaining({ x: 1, y: 1 }))
  .mockReturnValue('success')