Uncaught The email address is already in use by another account?

Question

JavaScript

I'm trying to test a function that fetches data from firebase. I am using Chai + Mocha for testing purposes. But I get an error when I start testing: "Uncaught The email address is already in use by another account". In firebase console, authorization is allowed. The data that the function needs returns
The function I'm trying to test:

funka

const getDbSnapshot = () => {
    return firebase.database().ref().once('value');
};

And the code I'm actually testing:

Test

describe('getDbSnapshot', () => {
    it('Should be not empty and with appropreate fields', (done) => {
        getDbSnapshot().then((res) => {
            const snapshot = JSON.parse(JSON.stringify(res));

            assert.exists(snapshot, 'Snapshot does not exist');
            assert.exists(snapshot.clients, 'Clients does not exist');
            assert.exists(snapshot.partners, 'Partners does not exist');
            done();
        });
    });
});

Plus a screenshot of the entire error in the console