Cannot find module 'firebase-admin' from 'index.cjs.js' - firebase

Question

I was using #firebase/testing on Jest, but since it's deprecated and instructed to use new one, I decided to move to #firebase/rules-unit-testing.
Here is the code where I just switched them.
import { initializeAdminApp } from "#firebase/rules-unit-testing";
import "babel-polyfill";
it("is ok", async () => {
const admin = initializeAdminApp({ projectId: "my-project" });
try {
const doc = admin.firestore().collection("items").doc("item-1");
await doc.set({ name: "Item 1" });
const ss = await doc.get();
expect(ss.data()?.name).toBe("Item 1");
} finally {
await admin.delete();
}
});
When I run this test with emu, it results "Cannot find module 'firebase-admin' from 'index.cjs.js'" error.
Cannot find module 'firebase-admin' from 'index.cjs.js'
3 |
4 | it("is ok", async () => {
> 5 | const admin = initializeAdminApp({ projectId: "my-project" });
| ^
It passes if it is the old #firebase/testing.
What did I miss?
Node.js v14.8.0
Jest 25.5.4
firebase 7.21.1
firebase-tools 8.11.2
#firebase/testing 0.20.11
#firebase/rules-unit-testing 1.0.4

Answer 1

The firebase-admin is an npm package. Just installed it and all worked.
$ npm install -D firebase-admin

Answer 2

I started to use firebase-admin#^10.0.1 and I had this error when running jest tests. It couldn't map "firebase-admin/app" to "firebase-admin/lib/app" as expected. So I have mapped this manually on jest.config.ts:
import { pathsToModuleNameMapper } from 'ts-jest/utils';
import { compilerOptions } from './tsconfig.json';
...
export default {
...
moduleNameMapper: pathsToModuleNameMapper(
{
...compilerOptions.paths,
'firebase-admin/*': ['node_modules/firebase-admin/lib/*'],
},
{
prefix: '<rootDir>',
},
),
...
}
That worked for me.
And just to note, my tsconfig.json is like this:
{
"compilerOptions": {
...
"baseUrl": ".",
"paths": {
"modules/*": [
"src/modules/*"
],
"shared/*": [
"src/shared/*"
],
}
}
}