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
- This slides
https://slides.com/jensknipper/greenmail - Demo code
https://github.com/JensKnipper/greenmail-example
- GreenMail
https://greenmail-mail-test.github.io/greenmail/ - Casper email sequence
https://www.indiehackers.com/post/what-a-great-email-sequence-looks-like-34e7d9a43c - TestPyramid
https://martinfowler.com/bliki/TestPyramid.html
GreenMail
By Jens Knipper
