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https://github.com/thekashey/jest-typed-mock
Be safe!. And use the force of TS/Flow to make mocks better.
https://github.com/thekashey/jest-typed-mock
flow jest mock mocking typescript
Last synced: 3 months ago
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Be safe!. And use the force of TS/Flow to make mocks better.
- Host: GitHub
- URL: https://github.com/thekashey/jest-typed-mock
- Owner: theKashey
- Created: 2017-11-29T07:54:42.000Z (about 7 years ago)
- Default Branch: master
- Last Pushed: 2018-05-27T07:32:44.000Z (over 6 years ago)
- Last Synced: 2024-04-29T22:17:37.903Z (10 months ago)
- Topics: flow, jest, mock, mocking, typescript
- Language: JavaScript
- Homepage:
- Size: 110 KB
- Stars: 7
- Watchers: 3
- Forks: 0
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
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README
# jest-typed-mock
## Make unit tests great again!
[](https://nodei.co/npm/jest-typed-mock/)
jest-typed-mock brings type checking to the wild `__mocks__` of Jest. Helping you maintain the correct mocks, matching the real files, they are going to mock.
This is like eslint, but for mocks.
``
Manual mocks are defined by writing a module in a __mocks__/ subdirectory immediately adjacent to the module. For example, to mock a module called user in the models directory, create a file called user.js and put it in the models/__mocks__ directory. ``
https://facebook.github.io/jest/docs/en/manual-mocks.html#content
# Usage
Add to your package.json
```json
"scripts": {
...
"jest-typed-mock": "jest-typed-mock flow", // for Flow
"jest-typed-mock": "jest-typed-mock typescript", // for TS
"jest-typed-mock": "jest-typed-mock javascript", // for JS
"jest-typed-mock": "jest-typed-mock exports", // only check names
...
}
```
In some cases (always?) you have to specify babel env.
# Type safety
[Rewiremock](https://github.com/theKashey/rewiremock) can provide a type safety to dependency mocking, but Jest do had it's own
mocking (and sandboxing) system. As long rewiremock still able to work, even under the Jest management - it is now a quite good idea.
__jest-typed-mock__ is not a library. It is just a small tool, which can check `mocked` file against the real one.
Lets imagine - we have a.js
```typescript
//a.js
export const function1 = (a:number):number => a**2;
export const function2 = (a:number):number => a*2;
export default (a:string) => a.substr(1)
```
and `__mocks__/a.js`
```typescript
export const function1 = (a:number):number => 1;
export const function2 = (a:number):number => 2;
export default (a:string) => "3"
```
It is ok. But next you change the real a.js
```typescript
//a.js
// function 1 is changed
export const function1 = (a:string):number => parseInt(a);
// function 2 is removed
export default (a:string) => a.substr(1)
```
But your tests are still using the old `__mocks__`, and they are still green.
__jest-typed-mock__ just matches real files and mocks.
### TS:
``
Property 'function2' is missing in type 'typeof "....a"'.
``
### Flow:
``property `function2` of exports of "/__mocks__/a.js". Property not found in const real = () => import('/a.js');``
### JS
As long there is no `types`, could only test exported names as their types(object, number, function), and function arguments count.
Even this is quite helpful.
``jest-typed-mock: mocked export "function2" does not exists in a.js``
jest-typed-mock will also try to check function agains function, at least argument count, which can break a lot of things.
To bypass this checking use
``jest-typed-mock exports``, or specify noFunctionCompare in API options
```js
require('jest-typed-mock/runjs')(__dirname , {noFunctionCompare: true})
```
# Result
As result - you reduce a smell of mocking. Mocks becomes less fake, and tests becomes less flake.
# Licence
MIT