If you useJest and you need to check that anArray contains anObject that matches a given structure,.toContain() won’t help you. So, a different approach is required.

Consider the following scenario. You have an array of objects:

const state = [
  { type: 'START', data: 'foo' },
  { type: 'START', data: 'baz' },
  { type: 'END', data: 'foo' },
]

… and you want to test that it contains an item like this{ type: 'END' } .

You could write the following test:

expect(state).toEqual(          // 1
  expect.arrayContaining([      // 2
    expect.objectContaining({   // 3
      type: 'END'               // 4
    })
  ])
)

The above reads as:

1. you expect that your Array equals
2. an Array that contains
3. an Object that contains
4. the following properties

NOTE:expect.arrayContaining() must be passed anArray[] even if you pass one item.

Adding it as a custom matcher

As

suggested, if you use this frequently, you might want to create acustom matcher, to avoid the verbose implementation: