Using Jest SAM Local Environment

jest-environment-samlocal.js

const { spawn } = require('child_process');
const NodeEnvironment = require('jest-environment-node');
const { timeout, TimeoutError } = require('promise-timeout');

class SamlocalEnvironment extends NodeEnvironment {
  constructor(config) {
    super(config);
  }

  async setup() {
    await super.setup();
    await this.setupSam();
    this.global.samlocal = true;
  }

  async teardown() {
    this.global.samlocal = undefined;
    await this.teardownSam();
    await super.teardown();
  }

  runScript(script) {
    return super.runScript(script);
  }

  // private

  async setupSam() {
    this.server = await this.spawnSamPromise();
  }

  async teardownSam() {
    if (this.server) { this.server.kill('SIGINT'); }
  }

  spawnSamPromise() {
    return timeout(new Promise((resolve, reject) => {
      let debug = false; // Change if you want logs. Good when you update SAM.
      let env = Object.create(process.env);
      env['DEBUG'] = '0';
      env['STAGE'] = 'test';
      env['NODE_ENV'] = 'test';
      env['AWS_PROFILE'] = undefined;
      let args = [
        'local',
        'start-api',
        '--port',
        '3022',
        '--template',
        './template.yaml',
        '--log-file',
        './log/test.log',
        '--env-vars',
        './.env.test.json',
        '--docker-volume-basedir',
        process.env.DIDPWD
      ];
      let server = spawn('sam', args, { env: env, cwd: '.' } );
      server.stdout.on('data', (data) => {
        let msg = data.toString();
        if (debug) { console.log('stdout', msg); }
      });
      server.stderr.on('data', (data) => {
        let msg = data.toString();
        if (debug) { console.log('stderr', msg); }
        if (/Running on/.test(msg)) { return resolve(server); }
      });
    }), 10000)
    .then((server) => { return server; })
    .catch((err) => { return; });
  }

}

module.exports = SamlocalEnvironment;