ReactJS - Can't import component

The import syntax without curly braces is for importing default exports, not for importing named exports.

Make your component the default export:

TestComponent.jsx

import React from 'react'

export default class TestComponent extends React.Component {

    render() {
        return (
            <div className="content">Test Component</div>
        )
    }
}

Alternatively you should be able to import it as it is with the following import statement:

import { TestComponent } from './components/TestComponent.jsx'

You might want to read up on ES6 modules (e.g. in Exploring ES6) if you want to use ES6 in your React code.