I am aware of how to mock/spy an ES6 import with jest , but this one gets around my head:
my-module.ts
import minimatch from 'minimatch';
export function foo(pattern: string, str: string): boolean {
return minimatch(pattern, str);
}
test.ts
:
describe('minimatch', () => {
it('should call minimatch', () => {
const mock = jest.fn().mockReturnValue(true);
jest.mock('minimatch', mock);
foo('*', 'hello');
expect(mock).toHaveBeenCalled();
});
});
I've also tried mocking in different way:
import * as minimatch from 'minimatch';
// ...
const mock = jest.fn().mockReturnValue(true);
(minimatch as any).default = mock;
Or even
import {mockModule} from '../../../../../../test/ts/utils/jest-utils';
// ...
const mock = jest.fn().mockReturnValue(true);
const originalModule = jest.requireActual('minimatch');
jest.mock('minimatch', () => Object.assign({}, originalModule, mockModule));
My test fails with all of the above ways to mock.
You can't use jest.mock()
inside test case functional scope. You should use it in the module scope.
Eg my-module.ts
:
import minimatch from 'minimatch';
export function foo(pattern: string, str: string): boolean {
return minimatch(pattern, str);
}
my-module.test.ts
:
import { foo } from './my-module';
import minimatch from 'minimatch';
jest.mock('minimatch', () => jest.fn());
describe('minimatch', () => {
it('should call minimatch', () => {
foo('*', 'hello');
expect(minimatch).toHaveBeenCalled();
});
});
Unit test results with 100% coverage:
PASS stackoverflow/60350522/my-module.test.ts
minimatch
✓ should call minimatch (6ms)
--------------|---------|----------|---------|---------|-------------------
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
--------------|---------|----------|---------|---------|-------------------
All files | 100 | 100 | 100 | 100 |
my-module.ts | 100 | 100 | 100 | 100 |
--------------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests: 1 passed, 1 total
Snapshots: 0 total
Time: 4.304s, estimated 6s
If you want to mock module inside test case, you should use jest.doMock(moduleName, factory, options) .
Eg
my-module.test.ts
:
describe('minimatch', () => {
it('should call minimatch', () => {
jest.doMock('minimatch', () => jest.fn());
const { foo } = require('./my-module');
const minimatch = require('minimatch');
foo('*', 'hello');
expect(minimatch).toHaveBeenCalled();
});
});
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