Access js script in header from jest

Question

I have this React application (cra) which embeds a script in its header. I use React Helmet for that.

I.e., In App.js I have this :

<GlobalContext.Provider>
    <Helmet>
        <script type="text/javascript" src={process.env.PUBLIC_URL + "/xmllint.js"}></script>
    </Helmet>
    <ThemeProvider theme={darkTheme}>
        <Dashboard/>
    </ThemeProvider>
</GlobalContext.Provider>

Anywhere in my typescript/javascript code, I have access to window.validateXML which is the function declared in xmllint.js.

(The reasons why I did this instead of an import is because I never figured out how to make this raw import play nice with the rest of the toolchain, and after trying for 3 days straight, I went with this option which is ugly but works).

However, when writing tests with Jest, the framework somehow does not see this global import, no matter how I tweak it.

C:\Users\me\source\ [unit_test ≡ +0 ~2 -0 !]> npm t -- --watchAll=false --json --outputFile=results.json
 FAIL  src/tests/MyTest.test.js (6.3 s)
  ● has access to validateXML

    TypeError: validateXML is not a function

      50 |      // XSD validation
      51 |      const xsd = await(await fetch('Test.xsd')).text()
    > 52 |      const res = validateXML({
         |                  ^
      53 |              xml:fileContent,
      54 |              schema: xsd,
      55 |              arguments: ["--noout", "--schema", 'Test', fileName]

      at ParseInputFile (src/Logic.tsx:52:14)
      at uploadXML (src/Logic.tsx:138:17)

This is what the test looks like

it('has access to validateXML', async () => {
  const user = userEvent.setup()
  render(
    <GlobalContext.Provider>
      <Helmet>
        <script type="text/javascript" src={"/xmllint.js"}></script>
      </Helmet>
      <Router>
        <MyComponentThatAccessesValidateXML>
      </Router>
    </GlobalContext.Provider>
  )
  let fileUploadButton = screen.getByRole('button', {name:'Upload XML'})
  const file = new File([xmlScenario], 'scenario.xml', {type: 'application/xml'})
  expect(fileUploadButton).toBeVisible()
  await waitFor(() => user.upload(fileUploadButton, file))
})

So the script is added to the header just like in App.js.

Things I have tried :

• Setting the script src to point to the location of xmllint.js relatively to the current file
• Setting the script src to xmllint.js
• Setting the script src to /xmllint.js
• Importing the content of xmllint.js via import or require
  • import {validateXML} from "xmllint"
  • import validateXML from "xmllint"
  • import {validateXML} from "xmllint.js"
  • import {validateXML} from "xmllint.js"
  • import {validateXML} from "../../public/xmllint"
  • import {validateXML} from "../../public/xmllint.js"
  • const validateXML = require("xmllint.js")
  • const validateXML = require("xmllint")
  • const validateXML = require("../../public/xmllint")
  • const validateXML = require("../../public/xmllint.js")
  • All of those attempts failed, i.e., validateXML was an empty object or undefined.

What can I do so my test sees the import validateXML that should be available globally ?