The sample code of unit test Lambda function in Serverless Framework projects .

test.js

const path       = require('path'),
      chai       = require('chai'),
      should     = chai.should(),
      Serverless = require('serverless')
      
describe('ServerlessProjectTest', function() {
  beforeEach(function(done) {
    this.timeout(0);

    s = new Serverless();

    s.init().then(function() {
      s.config.projectPath = __dirname + '/../';
      s.setProject(new s.classes.Project({
        stages: {
          dev: { regions: { 'ap-northeast-1': {} }}
        },
        variables: {
          project: 'serverless-project',
          stage: 'dev',
          region: 'ap-northeast-1'
        }
      }));
      
      s.getProject().setFunction(new s.classes.Function(
        {
          name:"hello",
          runtime:"nodejs4.3"
        },
        __dirname + '/../hello/s-function.json'));
 
      done();
    });
    
  });
  
   describe('#funciton hello()', function() {
    it('should be funciton hello success', function() {
      return s.getProject().getFunction('hello').run('dev', 'ap-northeast-1', {})
      .then(result => {
        result.response.message.should.equal('Go Serverless! Your Lambda function executed successfully!')
      });
    });
  });
});