Functional Programming tools in Golang that use Go 1.18 Generics

General Purpose tools for Functional Programming

  • Generic set operations on Golang arrays: Filtering, Union, Intersection, Minus
  • Generic Linked List
  • Generic function composition
  • Generic sort
  • Generic function currying and partial application

Type-Checked Properties-based testing that is based upon ScalaCheck and Haskell Quickcheck

  • Everything has strong typing thanks to Golang Generics.
  • Many kinds of test data generators
  • Every generator is composable. Lots of generators are included already and new ones are easy to make as compositions of existing generators.
  • A property is composable with other properties
  • Assertions are composable with And and Or logic
  • Test Failures include the specific generated values that caused test failure as well as the last successful case.
  • Programmers can better cover the scope of all possible inputs to a test (i.e. zero values, empty things, etc).
  • Tests outcomes are reproducible
  • Programmers can eliminate a lot of code duplication and get better tests at the same time because properties-based testing uses random test data.
  • Properties-based testing is useful for all sorts of tests: unit, integration, course-grained functional/system/black-box.

A few properties-based testing library exist in Golang. Gopter is an example. This library has much less code than Gopter and provides a very important feature that Gopter does not, namely that all abstractions are fully composable.

Two Key Abstractions

  • Generators – Generators are functions that produce random test data.
    • They are composable. You can combine them to make other generators.
    • They obey algebraic laws. You can guarantee the safety of their compositions.
    • They are pure functions, freely shareable between Go Routines.
    • Generators allow you to reproduce the exact same test data by passing in the same integer seed value into a SimpleRNG. You should never need to save files of test data again.
  • Properties – Properties are functions that execute a predicate-like function over a set of test data generated using a given Generator.
    • They are composable – You can combine them in arbitrary ways to make new properties.
    • They obey algebraic laws so that you can guarantee the safety of their compositions.
    • They are pure functions, freely shareable between Go Routines.
    • A property is a function that takes two function arguments:
      • one transforming a generated value into a potentially different type
      • and one evaluating the preceding value for correctness.
      • These two characteristics are a very important feature for test reuse.

Initializing Project

  • go1.18rc1 mod init pkg
  • go1.18rc1 mod tidy
  • go1.18rc1 test -v -count=1 ./...


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