Module not found: Error: Can't resolve

Why does this error occur and how can I fix it?

ERROR in ./src/index.ts
Module not found: Error: Can't resolve './test' in '/Users/maks/Documents/MyProgramms/TestProject/src'
 @ ./src/index.ts 3:13-30

Project file structure:

Index.ts

import { User } from './test';
let user = new User('ivan');

Test.ts

export class User {
    name: string;

    constructor(name:string) {
        this.name = name;
    }
}

Package.json

{
  "name": "testproject",
  "version": "1.0.0",
  "description": "",
  "main": "src/index.ts",
  "scripts": {
    "build": "webpack --mode development --open"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {},
  "devDependencies": {
    "@types/es6-shim": "^0.31.37",
    "@types/express": "^4.16.0",
    "ts-loader": "^4.4.2",
    "typescript": "^2.9.2",
    "webpack": "^4.12.0",
    "webpack-cli": "^3.0.8",
    "webpack-dev-server": "^3.1.4"
  }
}

Webpack.config.js

module.exports = {
    entry: {
        main: './src/index.ts'
    },
    module: {
        rules: [
            {
                test: /\.js$/,
                exclude: /node_modules/,
                    use: {
                    loader: "babel-loader"
                }
            },
            {
                test: /\.ts$/,
                exclude: /node_modules/,
                loader: 'ts-loader'
            },
        ]
    },
    node: {
        fs: 'empty',
        net: 'empty'
    },
    target: 'node'
};

I also tried importing via require, using awesome-typescript-loader, and updating webpack to the latest version.