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TDD 101
2. TDDing Value Objects
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TDDing Value Objects
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Value Object
(DDD)
Small object
Represents a concept
Equality based on value
Immutable:
• Should be created consistent
• Mutators should return new instances
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So… How do you TDD a VO?
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TDD VO Think of an invalid example
Write a test that fails expecting exception
Make the test pass
Repeat as needed to test invalid cases
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TDD VO Think of a valid example
Write a test that fails asserting value
Make the test pass
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TDD VO
Equality
Write a test that fails expecting inequality
Make the test pass
Then write a test that fails expecting
equality
Make the test pass
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TDD VO
Immutability
Think of a valid example of a mutator
Write a test that fails expecting a different
instance
Make the test pass
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