javascript - How can I test for object keys and values equality using Jest? - Stack Overflow

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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?

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?

• javascript
• unit-testing
• jestjs

Share Improve this question Follow edited Oct 5, 2022 at 7:43 Liam 29.5k2828 gold badges137137 silver badges200200 bronze badges asked Dec 11, 2017 at 14:11 fasenbergfasenberg 3,08533 gold badges1212 silver badges1616 bronze badges

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6 Answers 6

Sorted by: Reset to default 293

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

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

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

Just adding this tip, thought it gave even better granularity to my own tests, especially when matching against arguments to mocked services:

expect.objectContaining({
   url: expect.stringContaining('https://'),
})

Alternatively, you can use regex with expect.stringMatching which tests the given regex against the value. Pretty neat.

expect.stringContaining expect.stringMatching

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);

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.

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