Configurando el entorno de pruebas para nuestro proyecto

Ahora si ya empezó lo bueno

jest.config.js para typescript:

/** @type {import('ts-jest').JestConfigWithTsJest} */
function makeModuleNameMapper(srcPath, tsconfigPath) {
	// Get paths from tsconfig
	const { paths } = require(tsconfigPath).compilerOptions;

	const aliases = {};

	// Iterate over paths and convert them into moduleNameMapper format
	Object.keys(paths).forEach((item) => {
		const key = item.replace("/*", "/(.*)");
		const path = paths[item][0].replace("/*", "/$1");
		aliases[key] = srcPath + "/" + path;
	});
	return aliases;
}

const TS_CONFIG_PATH = "./tsconfig.json";
const SRC_PATH = "<rootDir>";

module.exports = {
	preset: "ts-jest",
	testEnvironment: "node",
	moduleNameMapper: makeModuleNameMapper(SRC_PATH, TS_CONFIG_PATH),
	modulePaths: ["<rootDir>"],
	rootDir: ".",
	moduleFileExtensions: ["js", "ts"],
};

y en tsconfig.json agrega:

"esModuleInterop": true