multiple-solutions.md

Multiple Solutions

You sometimes might want to implement multiple solutions to the same puzzle. For example to compare imperative vs. functional code styles, or test different data structures, or algorithms.

Since all these different implementations solve the same puzzle, they should have identical test cases. The AdventSpec is designed to test a single Solution at a time. However, that doesn't mean you need to duplicate the test code! You can instead define an abstract specification for your test cases, and use it to derive test classes for however many implementations!

You can use abstract classes to define the same test cases for multiple implementations.

Example

Let's learn by (trivial) example. Assume the fictitious puzzle, in which part one is supposed to add numbers, and part two to multiply them. We have two implementations (omitted for brevity), SolutionA and SolutionB.

The test classes are defined in the same way, each annotated by an @AdventDay annotation. However, instead of extending an AdventSpec directly, they instead extend an intermediary abstract class, which defines the test cases once.

This method ensures all solutions to a puzzle run against the same tests, and you can add as many solutions as you want, at the low-low cost of two lines of boilerplate a piece.

Full code sample:

object SolutionA : Solution { /* ... */ }
object SolutionB : Solution { /* ... */ }

@AdventDay(9999, 1, "Magic Numbers", "Variant A")
class SolutionATest : Y9999D01Spec<SolutionA>()

@AdventDay(9999, 1, "Magic Numbers", "Variant B")
class SolutionBTest : Y9999D01Spec<SolutionB>()

abstract class Y9999D01Spec<T : Solution> : AdventSpec<T>({
    partOne { "1,2,3,4" shouldOutput 10 }
    partTwo { "1,2,3,4" shouldOutput 24 }
})

You can provide a variant argument to the @AdventDay annotation. This is purely for aesthetics when using spec name formatting. {style="note"}