# Qualified

• Unit testing concept
• F.I.R.S.T. principles

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# Unit testing concept

• unit is the smallest testable part of an application (function, class, module, component)
• each test case is independent from the others (mocks, stubs)
• tests that impact the behavior of the system.

# Advantages

• The goal of unit testing is to isolate each part of the program and show that the individual parts are correct
• finds problems early in the development cycle
• allows to refactor code or upgrade system libraries at a later date, and make sure the module still works correctly
• provides a sort of living documentation of the system.
• cost of fixing a defect detected during unit testing is lesser
• debbuging is easy

# Disadvantages

• difficulty of setting up realistic and useful tests.
• 2 tests for each if(){}
• not easy for not pure function

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# F.I.R.S.T. principles of Unit tests

• Fast - many 100 or 1000 per seconds

• Isolates - failure reasons become obvius

• Repeatable - run repeatedly in any order, any time, any env

• Self-validating - no manual evaluation required, only pass/fail status

• Timely - written before the code