Test to Break Principles

There are two types of tests a developer can write, ‘test to work’ and ‘test to break’. Both are essential to robust development, but many developers only use the former and not the latter. This talk explains why ‘test to break’ principles are essential to ensure robust application development.

Transcript

1. W: rbrt.wllr.info | T: @RobDWaller
   Test to Break
   Principles
   Why You Should Crash Your Car Into a Tree
   

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   What is a Unit Test?
   

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   3 Types of Test
   

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   TDD Tips
   Test Business Logic
   Test Private Methods
   Test Input / Output
   Test Big Methods
   Do Don’t
   

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   Test to Work
   

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   Example 1.
   Given the driver has a valid car key.
   When they insert the key into the ignition.
   And they turn the key.
   Then the car's engine starts.
   

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    Example 2.
    Given the driver has an invalid car key.
    When they insert the key into the ignition.
    And they turn the key.
    Then the car's engine will not start.
    

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    Test to Break
    

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    Example 1.
    Given the driver has a screwdriver.
    When they insert it into the ignition.
    And turn the screwdriver.
    Then the car's engine will not start.
    

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    Example 2.
    Given a car is traveling at 30 mph.
    When it hits a tree.
    Then all the seat belts tighten.
    And the airbags deploy.
    

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    Code Example
    

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    Good software
    functions well and
    is bug free.
    

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    Ignorance Complexity
    

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    Ignorance is natural
    Complexity is standard
    Test to break helps
    

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    Rules
    1. Cars can only be black.
    2. Cars can have two or four doors.
    3. Cars must have four wheels.
    

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    Summary
    ‘Working’ software is not good enough.
    Writing good software is hard.
    You are ignorant.
    Your problems are complicated.
    Always write tests.
    Stress and break your business logic.
    Code will work in one way always.
    

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    Rob Waller
    T: @RobDWaller
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