Testing of email notifications with GreenMail, a mock mail server

Motivation

TestPyramid

Unit

Integration

e2e

Manual

€€€

€

TestPyramid for email notifications

  • avoid where possible
  • styled HTML Mails
  • smoke tests
  • happy paths
  • mail server communication
  • sending & receiving mails
  • triggers
  • mail content

Unit

Integration

e2e

Manual

Status quo - manual testing

  • no email server
    • error
    • write emails into log
       
  • production email server
    • change all email addresses
    • list of allowed recipients
  • testing not possible
  • digging in the logs
  • testing HTML mails not possible
  • danger of leaks​
  • connection needed​
  • resource allocation
  • many notifications in large teams
  • environment agnostic​ code​

Status quo - automatic testing

  • no e2e tests
  • no integration tests
  • Unit test
    • triggers & conditions
    • mail content

GreenMail

  • intial release: ~2006​
  • latest release: April 2021​
  • enables email integration testing​
    • sending mails​
    • receiving mails
  • prevents accidental email leaking to real email servers​
  • embeddable as dependency or runnable as email server​

Demo

GreenMail in the TestPyramid

Unit

Integration

e2e

Manual

Advantages using GreenMail

  • no digging in the logs​
  • testing Text and HTML mails easily​    
  • no fear of leaks​    
  • same code in all environments​    
  • all local​    
    • no network connection needed​    
    • receive your own mails only​    
    • local (hardware) resources

Further reading & sources​