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Created June 10, 2011 09:56
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Greg Young's Probability Kata
Value objects are an important concept in DDD. This kata is made both to learn value objects and to learn better ways of testing.
Write a probability value object. It should contain the following methods:
Probability CombinedWith(Probability)
Probability InverseOf()
Probability Either(Probability)
if you forget your probability math:
Either:P(A) + P(B) - P(A)P(B)
CombinedWith: P(A)P(B)
InverseOf: 1 - P(A)
The math is surprisingly not the main part of the exercise.
The internal state should be held as a decimal. Use TDD when writing this object.
One last thing. You can't put any getters on the object. What's the first test to write?
When finished continue reading:
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Probability InverseOf(Probability)
Probability InverseOf()
or do you intend it to be static?

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You are correct. Updated.

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