Sunday, December 25, 2011

Announcing FsUnit 1.0

A couple of weeks ago I announced a few enhancements to FsUnit. Today, I'm proud to announce the release of FsUnit 1.0. Version 1.0 includes support for additional testing frameworks, a new assertion function, and more...

New Testing Framework Support:

All previous releases of FsUnit provided support for only NUnit; however, the goal for FsUnit has always been to provide support for other major testing frameworks as well. This release largely accomplishes this goal by adding support for MbUnit version 3.3.454.0 and xUnit.NET version While the majority of functions provided for NUnit are also provided for these two testing frameworks, there are a couple of features that are not available. Each of these missing features can easily be worked around and the FsUnit unit tests provide examples of this.

NuGet Packages:

The easiest way to get started with FsUnit is to install one of the following NuGet packages.

- FsUnit for NUnit can be installed via the original NuGet package ID of FsUnit.
- FsUnit for xUnit.NET can be installed via the FsUnit.xUnit package ID.
- FsUnit for MbUnit can be installed via the FsUnit.MbUnit package ID.
Additional Assertion:

In addition to support for MbUnit and xUnit.NET, the equalWithin function has been added. Thanks to erdoll for requesting this enhancement and for providing much of the code for the NUnit implementation. The equalWithin function allows an equality assertion with a specified tolerance. Examples are provided below:

NUnit Example:
module Test.``equalWithin assertions``

open NUnit.Framework
open FsUnit

let ``should equal within tolerance when less than``() =
    10.09 |> should (equalWithin 0.1) 10.11

let ``should not equal within tolerance``() =
    10.1 |> should not ((equalWithin 0.001) 10.11)
xUnit.NET Example:
module Test.``equalWithin assertions``

open Xunit
open FsUnit.Xunit

let ``should equal within tolerance when less than``() =
    10.09 |> should (equalWithin 0.1) 10.11

let ``should not equal within tolerance``() =
    10.1 |> should not ((equalWithin 0.001) 10.11)
MbUnit Example:
module Test.``equalWithin assertions``

open MbUnit.Framework
open FsUnit.MbUnit

let ``should equal within tolerance when less than``() =
    10.09 |> should (equalWithin 0.1) 10.11

let ``should not equal within tolerance``() =
    10.1 |> should not ((equalWithin 0.001) 10.11)
Now on GitHub:

Last but not least, an FsUnit GitHub site is now available at FsUnit has had several contributors with submissions ranging from inception and NUnit implementation by Ray Vernagus, to major and minor enhancements, to examples and documentation. I hope that this move to GitHub will spur additional collaboration. The GitHub site will now act as the primary place for development and collaboration, while the CodePlex site will house major releases. We would love to have additional features and contributors, so jump on over and submit a pull request.

On to the Next One...

We are already working on the next release of FsUnit. Rodrigo Vidal has submitted a few new NUnit assertions--which will be ported to the MbUnit and xUnit.NET implementations where possible. Additionally, there have been discussions of pulling in Phillip Trelford's F# friendly Mocking library

Where would you like to see FsUnit go? We'd love to hear from you!

Saturday, December 10, 2011

Porting Bryan's Erlang Function to F#

A week or two ago, Fresh Brewed Coder Bryan Hunter posted a video to explain how to debug Erlang apps. In the tutorial, he stepped through a recursive function to display the various concepts. I thought it would be interesting to take that simple example and explore a few ways to write it in F#. Let's start by reviewing Bryan's example (which calculates the average of a provided list of number).

Here's what his average.erl source file looks like:


calculate(X) ->

calculate([H|T], Length, Sum) ->
     calculate(T, Length+1, Sum+H);

calculate([], Length, Sum) ->
Porting the Code to F#:

So how would you write this in F#? As with any language, there are several options. A fairly straight forward port might look like this:
let calculate x =
    let rec calc list length sum =
        match list with
        | head :: tail -> calc tail (length+1) (sum+head)
        | [] -> sum/length
    calc x 0 0
printfn "Value is %O" (calculate [10;22])
Breaking it Down:

The above code defines the calculate function that takes a list of integers as a single argument.

Next, a recursive function (the "rec" keyword indicates that it is recursive) named calc is defined (line 2). This function takes a list of integers as the first argument, the current length as the second argument, and the current sum as the last argument.

At the heart of this recursive function is a pattern match against the provided list (line 3). Using something known as the cons pattern, the first pattern (line 4) attempts to decompose the provided list into a "head" (the first element in the list) and "tail" (the rest of the elements).

If the first pattern is a match, the calc function is called with the "tail" list as the first argument, the length value incremented by 1 as the second argument, and the result of the sum value combined with the first value from the list (i.e. the head) as the third argument. This continues until the list is empty, at which point the cons pattern no longer results in a match and the second pattern is evaluated.

By the time the second pattern (line 5) is evaluated, the match will succeed due to the list now being empty. This causes the average to be calculated (i.e. sum/length) and returned.

Line 6 kicks off the initial call to the calc recursive function with the initial list as the first argument and default length and sum values of 0.

Finally, the last line (line 7) kicks off the whole thing with the call to calculate the average of the numbers 10 and 22 (as used in Bryan's demo).

Another Approach:

While  the approach above is pretty compact, F# provides a library that contains a high-order function that makes this even easier. The following line of code will also calculate the average of the values in a list of integers:
[10;22] |> List.averageBy (fun number -> float number)

Thursday, December 1, 2011

Enhancements to FsUnit (version

A new version ( of FsUnit -- a DSL for writing unit tests in F# -- is now available on the NuGet gallery.

This version includes the following improvements:

 - Libraries for frameworks 3.5 and 4.0.
 - Support for NUnit version
 - Several new functions including: greaterThan, greaterThanOrEqualTo, lessThan, lessThanOrEqualTo, shouldFail, endWith, startWith, and ofExactType.

Examples of the functions mentioned above are shown below:
module FsUnit.``Given a bunch of random tests``

open NUnit.Framework
open FsUnit

let ``When 11 it should be greater than 10``() =
    11 |> should be (greaterThan 10)

let ``When 11 it should be greater than or equal to 10``() =
    11 |> should be (greaterThanOrEqualTo 10)

let ``When 10 it should be less than 11``() =
    10 |> should be (lessThan 11)

let ``When 10 it should be less than or equal to 11``() =
    10 |> should be (lessThanOrEqualTo 11)

let ``When an empty List it should fail to contain item``() =
    shouldFail (fun () -> [] |> should contain 1)

let ``When fsharp it should end with rp``() =
    "fsharp" |> should endWith "rp"

let ``When fsharp it should start with fs``() =
    "fsharp" |> should startWith "fs"

let ``When 1 it should be of exact type int``() =
    1 |> should be ofExactType<int>

An example of what this looks like when run in Resharper's Test Runner is shown below:

A Side Note: If you haven't written many tests in F#, the lack of spaces in the test names may surprise you. This is a feature of F# that allows almost any sequence of characters to be enclosed in double-backtick characters (i.e. ``) and consequently treated as an identifier.

I hope you enjoy the latest enhancements to FsUnit. You can find the full source at

Building an ASP.NET MVC 4 Solution with F# and C#

There is a new project template available on Visual Studio Gallery for creating ASP.NET MVC 4 solutions with F# and C#. The current release of this project template allows creation of an empty ASP.NET MVC 4 web application (either ASPX or Razor), a F# project for controllers/models/etc., and an optional F# project that can be used to contain unit tests. The project creation wizard dialog box is shown below:

In the future, this template will be extended to include at least one additional project type.

To get the template, do the following (Note: Visual Studio 2010/11 Professional (or above) is required to use this template.):

1. In Visual Studio, navigate to File | New and select Online Templates.

2. Search for "fsharp mvc" and select the F# C# MVC 4 project template (see below):

The solution that was used to build this template can be found at