FP testing approach

Most of the case that's enough!

• Clean/Reinitiate properly between each test
• Coupling with other Module
• Mock some third-party dependencies
• Write multiple tests against the same function
• idempotence trouble

Only test our business logic data flow concern Observable context

RP approach marble-testing library

• Add additional endpoint
• Use middleware
• Pass user information through context

ASCII Art to define Observable and test it