Estoy tratando de probar mis componentes LitElement con Karma, pero la importación de PDF.JS hace que el archivo de prueba no se cargue.

Ejemplo del archivo del componente LitElement

 import * as pdfjsLib from 'pdfjs-dist/build/pdf.js'; import * as pdfjsWorker from 'pdfjs-dist/build/pdf.worker.entry.js'; import * as pdfjsSandbox from 'pdfjs-dist/build/pdf.sandbox.js'; import * as pdfjsViewer from 'pdfjs-dist/web/pdf_viewer.js'; import pdfjsViewerCss from 'pdfjs-dist/web/pdf_viewer.css'; export class UiDocReviewContext extends ScopedElementsMixin(LitElement) { static get properties() { return { ....

Ejemplo del archivo de prueba Karma

 import '../ui-doc-review-context.js'; describe('feat-upload', async () => { beforeEach(async () => { await fixture(html`<ui-doc-review-context .data=${{}} .pageNum=${1} .box=${{}} ></ui-doc-review-context>`); }); })

La cuestión
Karma da el siguiente error:

 Chrome Headless 100.0.4896.127 (Mac OS 10.15.7) ERROR: 'Error loading test file: /packages/ui-doc-review-context/test/ui-doc-review-context.test.js' Chrome Headless 100.0.4896.127 (Mac OS 10.15.7) ERROR: 'TypeError: Failed to fetch dynamically imported module: http://localhost:9876/base/packages/ui-doc-review-context/test/ui-doc-review-context.test.js?c2a0b72b2b28b1f3a57be6918056fed53cfcd90c'

En los registros de la consola me sale esto:

 Failed to load module script: Expected a JavaScript module script but the server responded with a MIME type of "text/css". Strict MIME type checking is enforced for module scripts per HTML spec. context.js:265 Error loading test file: /packages/ui-doc-review-context/test/ui-doc-review-context.test.js context.js:265 TypeError: Failed to fetch dynamically imported module: http://localhost:9876/base/packages/ui-doc-review-context/test/ui-doc-review-context.test.js?c2a0b72b2b28b1f3a57be6918056fed53cfcd90c