Dublin ALT.NET session Thu Oct 24 2013
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This document discusses using F# for testing .NET systems. It recommends using a test pyramid approach with more acceptance tests (AT) than unit tests (UT). It provides examples of how to write ATs using Gherkin syntax and the TickSpec BDD framework in F#. It also gives examples of unit testing with TickFacts and mocking libraries. The document notes some limitations of mixing F# and C# but recommends F# as a better language for testing due to its support for many paradigms and features useful for testing like tuples, lambdas, and quotations. It concludes with recommendations for books and resources on testing with F# and ATDD.
![TickSpec
TickFacts
[<TickFact>] let AdditionFeature () =
EmbeddedResourceFeatures.ScenariosFrom “Addition"
Step Definitions (TickSpec with unquote)
module CalculatorSteps =
[<When>] ``I add (.*) and (.*)`` x y =
result <- Calculator()
|> enter x |> plus |> enter y
|> compute
[<Then>] ``I should see (.*)`` expected =
test <@ expected = result @>](https://image.slidesharecdn.com/testingcinfdublinaltnet2013-131026023543-phpapp02/85/Dublin-ALT-NET-session-Thu-Oct-24-2013-7-320.jpg)
![Unit Testing
Tick methods (xUnit/NUnit with unquote)
module CalculatorFacts =
[<Fact>] let ``Adding two small ints works`` () =
let result = Calculator() |> enter 2 |> plus |> enter 2 |> compute
test <@ 2+2 = result @>
Mocking DSLs (Foq)
Mock<IList<char>>.With(fun x ->
<@ x.Count --> 2
x.Item(0) --> '0'
x.Item(1) --> '1'
x.Contains( any() ) --> true
x.RemoveAt( 2) ==> System.ArgumentOutOfRangeException()
@>)](https://image.slidesharecdn.com/testingcinfdublinaltnet2013-131026023543-phpapp02/85/Dublin-ALT-NET-session-Thu-Oct-24-2013-9-320.jpg)
Dublin ALT.NET session Thu Oct 24 2013
- 1. Testing . NET systems using F# HOW LONG WILL IT TAKE YOU? @RBARTELINK DUBLIN ALT.NET 24 OCTOBER, 2013
- 2. The test pyramid It’s not easy to achieve a good balance in a set of tests Too much AT -> slow + doesn’t drive implementation properly Too much UT -> Not meeting Living Documentation aim One size won’t fit all http://martinfowler.com/bliki/TestPyramid.html (originated by Mike Cohn)
- 4. Why? You need to express high and low level tests MbUnit, Sub/N/M/Spec are single paradigm 3 year old tests are uglier than 3yo production code Test code is just different to production code Learn a language a year F# has been in VS since 2009 One of F#’s many paradigms is to be a better C#
- 5. What can I use Everything (yes, everything) you know NUnit, MSpec, SpecFlow FluentAssertions, RhinoMocks, FakeItEasy, NSubstitute Things you’re already using xUnit.net, LINQ, Moq Modern Libs AutoFixture, AutoFixture.xUnit, AutoFixture.AutoMoq Foq, AutoFixture.AutoFoq TickSpec
- 6. Gherkin Feature files (Gherkin) Feature: Addition In order to avoid silly mistakes As a math idiot I want to be told the sum of two numbers Scenario: Add two numbers When I add 2 and 2 Then I should see 4
- 7. TickSpec TickFacts [<TickFact>] let AdditionFeature () = EmbeddedResourceFeatures.ScenariosFrom “Addition" Step Definitions (TickSpec with unquote) module CalculatorSteps = [<When>] ``I add (.*) and (.*)`` x y = result <- Calculator() |> enter x |> plus |> enter y |> compute [<Then>] ``I should see (.*)`` expected = test <@ expected = result @>
- 8. Gherkin Backgrounds and Outlines Feature: Addition Background: Given I switch my calculator to fancy mode Scenario Outline: The Hard Stuff When I add <First> and <Second> Then I should see <Total> Examples: |First|Second|Total| |1 |1 |2 | |9 |-1 |8 |
- 9. Unit Testing Tick methods (xUnit/NUnit with unquote) module CalculatorFacts = [<Fact>] let ``Adding two small ints works`` () = let result = Calculator() |> enter 2 |> plus |> enter 2 |> compute test <@ 2+2 = result @> Mocking DSLs (Foq) Mock<IList<char>>.With(fun x -> <@ x.Count --> 2 x.Item(0) --> '0' x.Item(1) --> '1' x.Contains( any() ) --> true x.RemoveAt( 2) ==> System.ArgumentOutOfRangeException() @>)
- 10. Low Level Stuff Type inference any() (for real) It.IsAny<DateTime>() mock() Mock.Of<T> Tuples let tuple = key,value let _,value = tuple var tuple = Tuple.Create( key, value) var value = tuple.Item2 Lambdas let gen a b = CreateSut a b |> Fill let gen = CreateSut >> Fill var gen = (int a, int b) => CreateSut( a, b).Fill() Object Expressions let time = { new ITime with member mock.GetHour() = 15} class FakeTime15 {int GetHour() { return 15;}} var time = new FakeTime15() Custom ops expected =? Actual // From unquote Asset.Equal( expected, actual) Quotations test <@ expected = result |> String.Concat “,” @> Assert.That( expected, Is.EqualTo( String.Concat( “,”, result))); let list = Mock<IList> .Method(fun x -> <@ x.Contains @>) .Returns( true) var mock = new Mock<IList>(); mock.Setup( x=> x .Contains( It.IsAny<object>()) .Returns( true)
- 11. The bad points Need to install FSC on CI server (2 clicks or 11 MB MSI or put FSC in tools dir Just Works) You can’t mix F# and C# in a single project F12 from F# to/from C# doesn’t work (but built in Ctrl-, and F12 within files is fine) No refactoring support of consequence (but not as important as you think) C# starts to grate a little more every day (as does “in F# you can just…”)
- 12. Books Growing Object Oriented Software, Guided by Tests (Freeman, Pryce) Specification By Example (Adzic) The RSpec book (Chelimsky et al) Expert F# 3 (Syme) Real World Functional Programming in F# and C# (Petricek, Skeet)
- 13. Resources F# @ptrelford http://trelford.com/blog and samples SO F# tag Google @tomaspetricek http://tomasp.net/blog/ Don’t forget MSDN ATDD GOOS @ploeh Outside In Test Driven Development http://pluralsight.com/training/Courses/TableOfContents/ou tside-in-tdd