Table Of Contents
Overview
Two Feedback Loops:
- Inner loop focuses on units of code and what they do.
- Outer loop focuses on the organization and the team. Ensuring that the application serves the users needs.
Dislike for testing comes from the fact that most people do not do as well with work they find uninspiring. Few developers enjoy testing their code and therefore arn't as good at it which then makes it less enjoyable to do because they're not as good at it. It's a vicious cycle.
Purposes Of Testing:
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Drive the quality of implementation (Does it work?)
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Drive the quality of the design (Is our code well structured?)
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What does well structured mean?
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Low coupling - when one object changes others don't have to change with it.
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High cohesion - objects have a single defined purpose/responsibility. They are not trying to do too many things at once.
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Makes us clarify the acceptance criteria, knowing when we have "completed" a feature.
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Allows us to catch regression error, making it easier to add new features with confidence.
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Adds an executable description of what code does
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Discourages us from adding functionality on top of what is really required.
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Makes it easier to refactor. Developers can then write code that communicates its purpose more effectively
Golden Rule of Testing: Never write new functionality without a failing test.
Acceptence: does the whole system work? Integration: does our code work against code we can't change? Like external libraries Unit: do our objects do the what we expect? are they a pleasure to work with?
Unit tests tell us about code quality but don't give us as much confidence about the system as a whole. Unit tests need to create the Object, its dependencies, send messages, and check that the behavior is as expected. In order for a class to be easy to unit test it inherently needs to be loosely coupled and highly cohesive.
Bloated Constructor: when instantiated an object becomes unweilding with the number of dependencies being injected, look for ways to naturally combine those dependencies to a higher level of abstraction and then use that abstraction in the object being tested.