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#unittesting

5 posts5 participants1 post today
Public
Ramin Honary
Property-based testing in Haskell with QuickCheck falsify

A few days ago, Edsko de Vries of Well-Typed published an in-depth article on property-based software testing, with a focus on the concept of “shrinking.”

In brief, property-based testing is sort-of like fuzz testing but for algorithms and protocols. Like fuzz testing, random test cases are procedurally generated, but unlike fuzz testing, the test cases are carefully designed to verify whether a software implementation of an algorithm satisfies a specific property of that algorithm, such as:

  • “this function always fails if the index is larger than the array”
  • “this function always returns a result in n*log(n) number of iterations for input dataset of size n“

  • “the sequence of log messages is guaranteed to obey this rules of this particular finite-state automata: (connect | fail) -> (send X | fail) -> (receive Y | receive Z | fail) -> success .”

Shrinking is the process of simplifying a failed test case. If you have found some input that makes your function return a value when it should have thrown an exception, or produce a result that does not satisfy some predicate, then that input is a “counterexample” to your assertion about the properties of that function. And you may want to be able to “shrink” that counterexample input to see if you can cause the function to behave incorrectly again but with a simpler input. The “QuickCheck“ library provides a variety of useful tools to let you define property tests with shrinking.

Defining unit tests with such incredible rigor takes quite a lot of time and effort, so you would probably do not want to use property-based testing for your ordinary, every-day software engineering. If you are, for example, being scrutinized by the US Department of Government of Efficiency, you would likely be fired if you were to take so much time to write such high-quality software with such a strong guarantee of correctness.

But if you are, for example, designing a communication protocol that will be used in critical infrastructure for the next 10 or 20 years and you want to make sure the reference implementation of your protocol is without contradictions, or if you are implementing an algorithm where the mathematical properties of the algorithm fall within some proven parameters (e.g. computational complexity), property-based testing can give you a much higher degree of confidence in the correctness of your algorithm or protocol specification.

www.well-typed.comfalsify: Hypothesis-inspired shrinking for Haskell
#tech#software#haskell
Continued thread
Public
Rachel Brindle

The testing attachments proposal has been accepted (with modifications)! To be attached to some upcoming swift version! forums.swift.org/t/accepted-wi

No real negative feedback, either. I guess people quickly became attached to the idea.

There were some disagreements about naming in the review, but I’m glad that we resolved that amicably. I’d really hate it if we were too attached to an idea to come to an agreement.

Swift Forums · [Accepted with Modifications] ST-0009: AttachmentsHello Swift community. The review of ST-0009: Attachments ran from March 20 through April 8, 2025. Feedback on the review was light but positive. There were some concerns about API naming. With that in mind, the Testing Workgroup has decided to accept this proposal with modifications. Specifically, we will change AttachableContainer to AttachableWrapper in order to avoid accidentally using the same term for unrelated features. Thank you to everyone who participated in this review for helping ...
#SwiftLang#swift#testing
Public
Rachel Brindle

Adding Attachments to Swift Testing is up for review! It's my first time being a review manager.

Forum thread: forums.swift.org/t/st-0009-att

Proposal: github.com/swiftlang/swift-evo

Swift Forums · ST-0009: AttachmentsHello Swift community, The review of ST-0009 "Attachments" begins now and runs through Tuesday April 8, 2025. The proposal is available here: swift-evolution/proposals/testing/0009-attachments.md at main · swiftlang/swift-evolution · GitHub Reviews are an important part of the Swift evolution process. All review feedback should be either on this forum thread or, if you would like to keep your feedback private, directly to the review manager. When emailing the review manager directly, please...
#SwiftLang#swift#testing
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