Jest UI React js components - unit tests - reactjs

Question

I am pretty new to React and Jest unit test framework. I have my component and trying to write few unit test cases , tried few ways and unable to proceed further. Here is my code and test case. Can anyone guide /suggest the best approaches please.
Non of the tests work and
Thanks
React UI component Header
import React from 'react';
import { Navbar, NavbarBrand } from 'reactstrap';
import { Link } from 'react-router-dom';
const Header = ({children}) =>
<Navbar light className="sticky-top navbar-expand-lg navbar-toggleable-sm bg-white border-bottom">
<NavbarBrand tag={Link} to="/">Abc: Customer Portal</NavbarBrand>
<div className="d-flex w-100 justify-content-end">
{children}
</div>
</Navbar>
export default Header
Tests - non of them pass, could anyone please guide me in the right direction.
import React from 'react'
import { Navbar, NavbarBrand } from 'reactstrap';
import renderer from 'react-test-renderer';
import { render, unmountComponentAtNode, ReactDOM } from "react-dom";
import { act } from "react-dom/test-utils";
import GlobalSettings from './../features/Header/GlobalSettings';
import UserDisplayName from './../features/Header/UserDisplayName';
import Header from './../features/Header/';
let container = null;
beforeEach(() => {
// setup a DOM element as a render target
container = document.createElement("div");
document.body.appendChild(container);
});
afterEach(() => {
// cleanup on exiting
unmountComponentAtNode(container);
container.remove();
container = null;
});
test('test Header component', () => {
//const nav = document.createElement('Navbar');
ReactDOM.render(<Header>
<Link to="/">Damage Matrix: Customer Portal</Link>
</Header>, Navbar);
ReactDOM.unmountComponentAtNode(nav);
});
test('test Header', () => {
act(() => {
render(<Header />, container);
});
expect(container.appendChild).toBe("Hello");
act(() => {
render(<Header children="GlobalSettings" />, container);
});
expect(container.textContent).toBe("GlobalSettings");
});
test('renders correctly', () => {
const tree = renderer.create(
<Header />
).toJSON();
expect(tree).toMatchSnapshot();
});