问题
I use typescript to write a simple demo with lit-html:
import {html, TemplateResult} from 'lit-html';
export default function sayHello(name: string): TemplateResult {
return html`<h1>Hello ${name}</h1>`;
}
and use jest to write some simple test:
import sayHello from "./sayHello";
import {render} from "lit-html";
beforeEach(() => {
render('', document.body);
})
describe('sayHello', () => {
it('says hello', () => {
render(sayHello('world'), document.body);
const component = document.querySelector('h1');
expect(component).toBeDefined();
})
})
My "jest.config.js" is:
module.exports = {
preset: 'ts-jest',
testEnvironment: 'jsdom',
}
But when I run the tests with jest
, I got such error:
FAIL src/sayHello.test.ts
● Test suite failed to run
Jest encountered an unexpected token
This usually means that you are trying to import a file which Jest cannot parse, e.g. it's not plain JavaScript.
By default, if Jest sees a Babel config, it will use that to transform your files, ignoring "node_modules".
Here's what you can do:
• To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.
• If you need a custom transformation specify a "transform" option in your config.
• If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.
You'll find more details and examples of these config options in the docs:
https://jestjs.io/docs/en/configuration.html
Details:
/workspace/typescript-webpack-lit-html-jest-test-demo/node_modules/lit-html/lit-html.js:31
import { defaultTemplateProcessor } from './lib/default-template-processor.js';
^^^^^^
SyntaxError: Cannot use import statement outside a module
> 1 | import {html, TemplateResult} from 'lit-html';
| ^
2 |
3 | export default function sayHello(name: string): TemplateResult {
4 | return html`<h1>Hello ${name}</h1>`;
at Runtime._execModule (node_modules/jest-runtime/build/index.js:1166:56)
at Object.<anonymous> (src/sayHello.ts:1:1)
at Object.<anonymous> (src/sayHello.test.ts:1:1)
Test Suites: 1 failed, 1 total
Tests: 0 total
Snapshots: 0 total
Time: 1.339 s
Ran all test suites.
error Command failed with exit code 1.
The reason should be the file in "node_modules" node_modules/lit-html/lit-html.js
uses es module, and jest can't handle it well.
I tried all kinds of configurations, but still can't fix it, need your help, thanks.
A small and complete demo project for this issue: https://github.com/freewind-demos/typescript-webpack-lit-html-jest-test-demo
回答1:
By default Jest doesn't transforms the /node_modules/
(docs). In order to make it work you can change your configuration like this
jest.config.js
module.exports = {
preset: "ts-jest",
testEnvironment: "jsdom",
transform: {
// transform files with ts-jest
"^.+\\.(js|ts)$": "ts-jest",
},
transformIgnorePatterns: [
// allow lit-html transformation
"node_modules/(?!lit-html)",
],
globals: {
"ts-jest": {
tsConfig: {
// allow js in typescript
allowJs: true,
},
},
},
};
来源:https://stackoverflow.com/questions/62200568/syntaxerror-cannot-use-import-statement-outside-a-module-when-writing-test-wi