Jest: how to test for object keys and values?

Question

I have a mapModule where I import components and export them:

import ComponentName from '../components/ComponentName';

export default {
  name: ComponentName,
};

How can I test that mapModule has the correct exported keys, values and that they are not null or undefined?

Answer 1

In version 23.3.0 of jest,

expect(string).toMatch(string) 

expects a string.

Use:

const expected = { name:'component name' }
const actual = { name: 'component name', type: 'form' }
expect(actual).toMatchObject(expected)

result is passing test

Answer 2

you can use one of those:

toEqual and toMatchObject are template matchers for objects:

let Obj = {name: 'component name', id: 2};
expect(oneObj).toEqual({name: 'component name'}) // false, should be exactly equal all Obj keys and values  
expect(oneObj).toMatchObject({name: 'component name'}) // true

or easly use toHaveProperty :

let Obj = {name: 'component name'};
expect(oneObj).toHaveProperty('name') // true
expect(oneObj).toHaveProperty('name', 'component name') // true

Answer 3

Keep in mind that .toMatchObject checks

"that a JavaScript object matches a subset of the properties of an object."

So toMatchObject can have unintended assertions such as:

expect({ a: 1, b: 2 }).toMatchObject({ a: 1 }); // pass

If you do want to match an object exactly, you should use .toStrictEqual, available since jest 23:

expect({ a: 1, b: 2 }).toStrictEqual({ a: 1 }); // fail

Answer 4

For a single key you can check out

expect(Boolean(obj[prop])).toBe(true | false);

For multiple key (where all must be present) you can use,

expect(Boolean(obj[prop1]) && Boolean(obj[prop2])).toBe(true | false);

For multiple key (where any one must be present) you can use

expect(Boolean(obj[prop1]) || Boolean(obj[prop2])).toBe(true | false);

Answer 5

Another way is to:

expect(JSON.stringify(object)).toBe(JSON.stringify(object))

This will ensure the objects are the same.

However using this:

expect(object).toMatchObject(object)

is the best option in most cases.