How can I test part of object using Jest?

Question

I would like to test that time is parsed correctly and I am only interested in checking some of the properties and not the entire object. In this case hour and minutes.

I tried using expect(object).toContain(value) but as you can see in the snippet below it fails although the object contains the properties I am interested in and they have the correct value.

● Calendar > CalendarViewConfig › it should parse time  expect(object).toContain(value)  Expected object:   {"display": "12:54", "full": 774, "hour": 12, "hours": 12, "minutes": 54, "string": "12:54"} To contain value:   {"hours": 12, "minutes": 54}    67 |   it('it should parse time', () => {   68 |     ... > 69 |     expect(parseTime('12:54')).toContain({ hours: 12, minutes: 54})   70 |   })    at Object.<anonymous> (src/Components/Views/Calendar/CalendarViewConfig.test.js:69:32) 

Answer 1

To check if expected object is a subset of the received object you need to use toMatchObject(object) method:

expect(parseTime('12:54')).toMatchObject({ hours: 12, minutes: 54}) 

or expect.objectContaining(object) matcher:

expect(parseTime('12:54')).toEqual(expect.objectContaining({ hours: 12, minutes: 54})) 

they works in slightly different ways, please take a look at What's the difference between '.toMatchObject' and 'objectContaining' for details.

toContain() is designed to check that an item is in an array.