How to make through Google's IAP in Cypress?

Question

I come with a question because I have an application, it has IAP as a proxy before seeing the rest of the page. I want to test this page, however, IAP is standing in my way. I'm trying to wade through the docs, but I don't understand which way of authentication I may need to use.

I tried with Application Default Credentials as I have that JSON auth file and env pointing at that, and after going to the site, I get a 403 that I can't access the site. Maybe I'm doing something wrong in general?

cypress.config.ts

import { GoogleAuth } from 'google-auth-library';
const GOOGLE_PROJECT_ID = 1234567;
async setupNodeEvents(on, config): Promise<Cypress.PluginConfigOptions> {
      // ... other functions, working with async/await

      on('task', {
        getIAPToken: async () => {
          console.log(' Initialized GoogleAuth');
          const auth = new GoogleAuth({
            scopes: ['https://www.googleapis.com/auth/cloud-platform'],
          });
          const client = await auth.getClient();
          const projectId = GOOGLE_PROJECT_ID;
          const iapUrl = `https://iap.googleapis.com/projects/${projectId}/iap_web/auth`;
          console.log(' Requesting IAP');
          const response = await client.request({ url: iapUrl });

          return response;
        },
      });

      return config;
    },

test.cy.ts

describe('Smoke tests', () => {

  it('content is not visible', () => {
    cy.visit("https://some-page-behind-iap.com");
    cy.contains("Content!").should(content => expect(content).to.not.be.visible;
  });

  it('content is visible', () => {
    cy.visit("https://some-page-behind-iap.com");
    cy.task('getIAPToken').then((data) => {
      console.log("loaded:", data);
    });
    cy.contains("Content!").should(content => expect(content).to.be.visible;
  });
});