Automatically loading Vim files from Dropbox folder

I have been a happy Dropbox user for a while now. I try to link whatever possible to it like:

  • Visual Studio settings
  • PowerShell modules
  • Resharper mounted live template file

Until today I was still copying my vimfiles back and forth though.

So I finally took the time to investigate how to point the vim runtimepath to a folder of my choice.

Turns out there are two ways to do this:

  1. Point the vim runtime path to a folder in your dropbox
  2. Create a link from your local vimfiles folder to the vimfiles folder in your dropbox

Point the vim runtime path to a folder in your dropbox

In this case vim itself (‘:help runtimepath’) was more helpful than stackoverflow and google.

This stackoverflow answer maybe useful to others, but in my case I never could get the printf() statemtent to work and I also would like to start vim without specifying the path every time.

As I said, the help helped (npi) and after a bit of experimentation I came up with this solution.

I added

set runtimepath=~/Dropbox/Settings/vimfiles,$VIM,$VIMRUNTIME

to my .vimrc file.

Note that for Windows the dropbox folder is called ‘My Dropbox’ and therefore you need to escape the space like so:

set runtimepath=~/Dropboxes/Gmail/My\ Dropbox/Settings/vimfiles,$VIM,$VIMRUNTIME

Now I could remove my .vim folder (vimfiles on Windows ) from my HOME directory and am picking up all my plugins, syntax highlighters, etc.  directly from the given vimfiles folder inside my Dropbox.

Only the .vimrc file has to stay were it is and will have to be synchronized among my computers since something has to do the pointing.

Create a link from your usual vimfiles folder to the vimfiles folder in your dropbox

I found a great explanation on how to do this on different operating systems.

Here is an example on how to do this on Windows:

  1. Make sure that all your vimfiles have been copied to your Dropbox folder.
  2. Remove the vimfiles in you HOME directory.
  3. Launch cmd.exe and use mklink to create a link from ~/vimfiles to the vimfiles in your dropbox e.g.:
    mklink /D "c:\Users\yourusername\vimfiles" "C:\Users\yourusername\My Dropbox\Settings\vimfiles"
  4. Optionally do the same for your .vimrc file (I actually link it to a window specific one, because I use a different font for each OS):
    mklink "c:\Users\yourusername\.vimrc" "C:\Users\yourusername\My Dropbox\Settings\.vimrc_windows"

    In this case you need to make sure to not directly edit the local .vimrc as this will overwrite the link you created. Instead edit the .vimrc inside your Dropbox folder.

Both solutions allow me to extend my vim, for all my machines in one shot.

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Go to specific parent directory with PowerShell

After typing commands similar to  ‘cd ..\..\..\’ a few too many times, I needed a better solution.

My first idea was to have something like cd… and depending on the number of dots go up to the nth parent. Still, I’d have to count how many directories up my target is.

A colleague of mine had a better idea:

Lets say you are in
and you would like to go to
Ideally you just type something like ‘cdto users‘ or even ‘cdto u


It would indeed be dandy to have such a function, so I invested some time and came up with the below implementation.

        Sets location to the first parent directory that whose name starts with the given target dir.
        Searches upwards to the root drive.
        If target dir is not found, a message is emitted to the console
        cd c:\user\joeshmoe\Documents 
        Set-LocationTo us 
function Set-LocationTo {            
    param(  [parameter(Mandatory = $true)]            
            [string] $targetDir)            
    $dirs = (pwd).Path.Split('\')            
    for($i = $dirs.Length - 1; $i -ge 0; $i--) {            
        if ($dirs[$i].ToLower().StartsWith($targetDir.ToLower())) {            
            $targetIndex = $i            
    if($targetIndex -eq 0) {             
        Write-Host "Unable to resolve $targetDir"             
    $targetPath = ''            
    for($i = 0; $i -le $targetIndex; $i++) {            
       $targetPath += $dirs[$i] + '\'             
    Set-Location $targetPath            
Set-Alias -Name cdto -Value Set-LocationTo

If you are sourcing this Set-Location.ps1 from within a module, make sure to export aliases as well e.g.:

Export-ModuleMember -Function * -Alias *

otherwise ‘cdto’ won’t be available.

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PowerShell and .svnignore

I got very tired of manually ignoring “bin”, “obj” folders and various files (e.g. _Resharper*) when using Svn.

So I looked for a better solution –  something similar to Git’s .gitignore.

Reading up on some svn documentation resulted in the below function that will look for ignore definitions (similar to .gitignore) in a given .svnignore file and apply these to all folders recursively.

$psd = Split-Path (Get-Variable MyInvocation).Value.MyCommand.Path            

function Ignore-Svn {            
    param(  [parameter(Mandatory = $true)]            
            $svnIgnoreFile = "$psd\.svnignore",            
            [switch] $recurse)            

    $fullPath = (Resolve-Path $path)            
    if($recurse) { $recFlag = "-R" }            
 svn propset svn:ignore $fullPath -F $svnIgnoreFile $recFlag            

Here is my .svnignore file:
Finally in order to add all new files that are not ignored, we can use the following function:

function Add-Svn {            
 svn st | %{ if ($_ -match "\?\s+(.*)") { svn add $matches[1] } }            


Svn and Git enabled PowerShell prompt

After reading this post and integrating it into my $PROFILE script I marveled at the nice git repository prompt.

A few days later I learned, that we will be using subversion on our next project. To remedy my sadness, my colleague Doug Finke pointed out his svn prompt.

That cheered me up, but since I didn’t want to keep changing my script every time I work with either git or subversion repositories, I combined both of them into a prompt, that gives me information about added(+), modified(~), deleted(-) and untracked(!) files.

I also applied few tweaks to make them more consistent.

Here the screenshots for the no repo, git repo and svn repo prompts:

You can find the script here.

In order for the git part to work you will need this gitutils file.

Amend: In the meantime I changed/improved the script a bit, so the prompts will look somewhat different than in the picture.

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TDD suggested readings

Lots of books about test driven development are out there.

In this post I will list the ones I found helpful.

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Using mockito in BDD

This post could also have been titled: How to avoid meta-tag-itis, as the main challenge when using mockito in a BDD approach is to avoid having to adorn every context class with all the mocks that it, or its base context creates.

In order to understand why these tags are even necessary I dug into the source code and came up with the workaround described below.

Mockito under the hood

Mockito is actually build up onto ASMock, another mocking framework.

ASMock in turn uses  FLoxy, a dynamic proxy generation library which was created for ASMock originally. In order for FLoxy to generate the byte code,  it uses the FLemit libraries.

Unfortunately the created byte code cannot just be added to the AVM (ActionScript Virtual Machine) on the fly. Instead this has to be done asynchronously before any mocks that use it are created.

As far as I could gather, this is how mockito proceeds:

  1. It reflects on the Test classes to find out for which interfaces/classes it will be required to supply mock objects
  2. It creates the byte codes for these, providing a success callback which kicks off the testrunner and a failure callback which will be called if something goes wrong
  3. once all byte code has been prepared, the success callback is invoked and mockito starts running the tests
  4. if we now request a mock for a certain type, it uses the prepared byte code to supply us with a new mock instance

Why meta-tags aren’t optimal

In order to perform the first of the above mentioned steps, mockito needs us to specify via meta-tags, what mocks we will need.

Unfortunately it is not enough to just put these tags on top of the context class that actually will instantiate them  via mock(IDependency)

Instead, every sub context class (the one containing the specs), that inherits from this context class will have to be adorned with it.

Here is an example:

public class when_something_is_the_case extends SomeSpecs
    [ ... ]

As you can see, the RunWith attribute also needs to be added.

Here are the disadvantages of doing it in this manner:

  • clutters up the code (imagine meta-tags for six mocks on every context class)
  • not refactor friendly – as strings and thus meta-tags never are
  • not very maintainable – every time I add another dependency that needs to be mocked, I have to add another meta-tag onto each context class

Clearly not the way to go.

The Mockito class

While digging inside the source code, I found the “Mockito” class which contains the following function:
public function prepareClasses(classes : Array, calledWhenClassesReady : Function, calledWhenPreparingClassesFailed : Function = null) : void

The trick is to use this class in our custom ContextsRunner to prepare the necessary mocks before we kick off the FlexUnit test runner.

This is done inside our runWithMockito function:

        private function runWithMockito(fakeClasses : Array) : void
		new Mockito().prepareClasses(fakeClasses, runContexts, handleFailure);

In case you are wondering why I am adding a dummy context. Looking at its code explains what is going on:

 * This class is included in the run contexts, to give mockito one test class
* which has the meta-tag that mockito looks for to initialize.
* Alternatively we could put it on one of our context classes, but this is more convenient. * @author tlorenz */ [RunWith("org.mockito.integrations.flexunit4.MockitoClassRunner")] class dummy_context_to_initialize_mockito { [Test] public function safely_ignore_this_little_hack() : void { } }

Fortunately this workaround is easier to use than to understand.

Using the ContextsRunner with mockito

As described in the previous post, we create an Air application to run our tests with mockito.

Inside the creationComplete handler we create a ContextsRunner instance and invoke its run method with the contexts to run and the mocks that need to be prepared by mockito:

    private function onCreationComplete() : void
	new ContextsRunner().run([context1, context2, ...], [ClassOrInterface1, ClassOrInterface1, ...]);

As a result we don’t need to put any meta-tags inside of our test project.

We only need to make sure, that we pass the class or interface of every mock that we will be requesting from mockito along.

As mentioned in the previous post, we also need to add this compiler argument:

  • -includes org.mockito.integrations.flexunit4.MockitoClassRunner

And of course we need to reference the mockito library

The dummy test will show up in our test results, but that should not pose a major problem.

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BDD with FlexUnit using workarounds

We will now improve on the methodology introduced in the previous post.

The source code for this approach is available here.

Make sure to add “-includes org.mockito.integrations.flexunit4.MockitoClassRunner” to the compiler arguments when compiling the test application.

Running specs inside private classes

Most of you will already know that it is indeed possible to include more than one class inside one ActionScript file.

The crux is that only one of them can be made public. The other ones need to be private and outside of any package. They are consequently only visible to classes within that same ActionScript file.

For that reason the FlexUnit test runner has no way of finding them and thus cannot run the contained specifications.

Here is what we need to do:

  1. find a way to make the private classes accessible outside their containing ActionScript file
  2. tell the FlexUnit test runner to run the specs inside them – this will require the creation of a custom runner

The first part is rather simple. All we need is a static property on our public class that returns an Array of the private classes contained inside the same ActionScript file.

To show how this works, here is the new and improved EmployeeSpecs class and some of the private classes contained within the same file:
Don’t worry about the mockito related code at this point as it is explained in a separate post.

	import accounting.interfaces.IBankAccount;

	import org.mockito.integrations.mock;

	import specutils.base.SpecificationsBase;

	public class EmployeeSpecs extends SpecificationsBase
		public static function get contexts() : Array
			return [

		protected var _bankAccount_Mock : IBankAccount;

		protected var _sut : Employee;

		override protected function context() : void
			_bankAccount_Mock = mock(IBankAccount);

			_sut = new Employee(_bankAccount_Mock);

import org.mockito.integrations.*;

class initially extends EmployeeSpecs

	public function should_not_have_been_paid() : void

	public function should_not_have_been_fired() : void

	public function should_have_zero_salary() : void

class when_told_that_he_is_fired extends EmployeeSpecs
	override protected function because() : void

	public function was_fired_should_return_true() : void

class Ctx_BankAccountIsConnected extends EmployeeSpecs
	override protected function context() : void

class when_bankaccount_is_connected_and_his_salary_is_1_dollar_paying_him extends Ctx_BankAccountIsConnected
	private const SALARY : int = 1;

	override protected function context() : void
		_sut.salary = SALARY;

	override protected function because() : void

	public function sets_wasPaid_to_true() : void


	public function should_update_his_bank_account() : void

	public function should_update_his_bankaccount_with_1_dollar() : void

The function public static function get contexts() : Array passes all specification classes to the outside world.

I called it contexts() to indicate that it actually returns an Array of classes, each containing a context definition and related specifications.

Calling it specifications() would not have been reflective of that fact.

It is important to note, that the class names contain information about the context and the action since now there are no more extra packages to convey part of this information.

Finally we need to find a way to tell FlexUnit to run the tests contained inside each class.

Creating a custom FlexUnit Test Runner

This task is actually easier than it seems. Still I only want to do it once, so I created a ContextRunner class.

It has a run method that takes an Array of context class Arrays (quite a mouthful) and an optional Array of dependencies that need to be prepared by mockito (we’ll get to that in the next post).

The run method collects the individual specifications, sorts them and finally passes them to the runContexts() method.

This method pushes those specifications into a FlexUntit Test runner and instructs it to run.

        private function runContexts() : void
		var testRunner : FlexUnitTestRunnerUI = new FlexUnitTestRunnerUI();
		testRunner.runWithFlexUnit4Runner(allContexts, "");


The second argument of the runWithFlexUnit4Runner() method is ideally the test project name.

This name will change for each test project though and passing in some name will throw an error after the test run completes  if it doesn’t match the name of the project that contains the tests.

Just passing an empty string avoids this annoyance.

You can to take a closer look at the ContextRunner which is contained inside the SpecUtils project.

Creating an Air test application

Since we have to use our custom test runner, we can no longer use the integrated “Execute FlexUnit tests” functionality as this will just kick off the default FlexUnit test runner, which will fail to find any of our tests.

Instead we transform our application itself into a test runner.

The steps are simple:

  1. Create an Air Application
  2. Inside the onCreation Event instantiate the custom ContextsRunner
  3. pass it our private context classes that we obtain via the static contexts properties from our Specs classes
  4. optionally pass any dependencies that need to be prepared by mockito
  5. run in debug mode (F11)

I chose to use an Air application to avoid a tab to be opened inside my browser that presents me with this:

The presented information it is not very helpful in itself and only gets in the way of  looking at the detailed information inside the FlexUnit Results tab.

One solution is to close all tabs on a browser which will cause the Flash Player to close the popup automatically, but as soon as I have a browser instance open anywhere, it brings it into view, adds its tab and leaves it open.

By using an  Air application to run my tests, I can set the window visibility to false and am never bothered by anything popping up.

Here is the <WindowedApplication>  file for our test application.

<?xml version="1.0" encoding="utf-8"?>
<s:WindowedApplication xmlns:fx=""
			import accounting.interfaces.IBankAccount;
			import accounting.interfaces.IEmployee;


			import mx.controls.Alert;

			import specutils.runners.ContextsRunner;

			private function get fakes() : Array
				return [IBankAccount, IEmployee];

			private function get allContexts() : Array
				return [

			private function onCreationComplete() : void
				new ContextsRunner().run(allContexts, fakes);


Referencing the FlexUnit libraries

When executing flex unit tests as intended by the FlashBuilder IDE, it will automatically add the FlexUnit libraries for you.

When we are using the just described approach instead, we can either add them manually, or trick FlashBuilder into doing it for us.

Just select “Execute FlexUnit Tests” from the menu. At that point the libraries will be added. In case FlashBuilder complains that there are no tests in our project, just add a dummy test inside any public class and try again.

After the libraries have been added, we delete the FlexUnit application that was created and the dummy test case (if we needed one).

Now we are ready to use the FlexUnit libraries in our test classes.


If we are using the SpecUtils library classes to run our tests and make our assertions, we don’t need to includethe FlexUnit libraries, since then there is no need to directly reference the classes contained in them.

What’s the catch?

There are actually two drawbacks to doing things as described.

  • Since we manually collect and run our specifications, we need to make sure to pass the containing classes out through our context property
    • if we forget to do this, the test runner will do just fine, but our newly added specs inside it are never executed
    • if we are following the Red-Green-Refactor process, this shouldn’t  be a problem, as we will notice that nothing failed, after we added another failing test
    • this will remind us to include the new context inside the Array that we pass out to the runner
  • The other drawback is due to the fact that the FlexUnitResult navigation does not work for private classes
    • clicking on a test inside the FlexUnit Results tab will produce an error message instead of navigating to the test
    • it’s no biggie though, since all we have to do is to open the main Specs class, look at the classes being passed out, find the one containing our test and press F3 to navigate to it



  • As Before:
    • ability to convey lots of information without verbose test names
    • contexts are built up incrementally and are centralized which makes for easier maintenance
    • specific/general contexts clearly communicate what is needed for individual/all specifications
    • actions and assertions are clearly separated into because() and [Test] methods
    • specifications are easy to read as they are one liners
  • no more file/package explosion
  • easier to navigate and thus easier to understand and follow for people not familiar with the concept


  • does not integrate fully with the FlexUnit framework and thus requires the creation of custom test runners
  • automatic navigation from test results to the related test code does not work

In the next post we’ll look at a way to make mockito part of our workflow in a way that works great with the described approach.

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BDD with FlexUnit using separate files

We will now try to remedy some of the problems of the methodology explained in the previous post.

Source code for this approach is available here.

Contexts, Because and Specifications

Lets first look at how our tests (or specifications as they are called in the behavior driven environment) are organized.


  • Main Context
    • usually we will create a context class that sets up the most general requirements in order to test a class.
    • at the least it will instantiate it and more often than not also inject its dependencies.
    • I usually name my main context classes after the class I’m testing with a “Specs” suffix e.g. “EmployeesSpecs” in order to communicate that it sets up at least part of the context used by all specifications for the Employee class
  • Context
    • any time that a sub context needs to be setup I will create a separate class for it and specifications that use it
    • this context inherits from the main context
    • additionally it sets up requirements needed to test the behavior that the specifications in the containing class need
    • there is a maximum of one context per class


  • contains the code that acts on the system under test after the context was fully specified
  • is optional and will not be present if no action is needed e.g. when some initial criteria need to be checked
  • there is a maximum of one because method per class


  • check the result(s) of the action inside the because method
  • there can be numerous specifications in one class
  • specifications should not act on or write to the system under test or its dependencies, but only read out the results
  • any actions needed should not be part of the specifications, but are performed inside the because method, therefore the specification methods will most likely be one liners

The SpecificationBase class

In order to help in BDD , I created a Specification base class which all my Main Contexts (Specs classes) will inherit from.

Essentially all it does is hide away the FlexUnit4 mechanics of preparing the tests and allows to set them up in a more BDD agnostic way.

It also includes a method which allows to write assertions in BDD lingo.

Don’t worry about the catchError() method for now.

Again, reading the comments will help in understanding how it works.

 2 package specutils.base
 3 {
 4     import specutils.extensions.SpecificationExtensions;
 6     /**
 7      * Acts as a base class for all specifications to help with BDD.
 8      *
 9      * @author tlorenz
10      */
11     public class SpecificationsBase
12     {
14         protected var caughtError : Error;
16         [Before]
17         public function setup() : void
18         {
19             context();
20             because();
21         }
23         /**
24          *
25          * @param actual the object whose value we are testing
26          * @return the actual object wrapped in a SpecificationExtensions class that adds methods like shouldEqual, shouldBeTrue, etc.
27          *
28          */
29         protected function the(actual : Object) : SpecificationExtensions
30         {
31             return new SpecificationExtensions(actual);
32         }
34         /**
35          * Sets up the context for the specs in the current class.
36          * IMPORTANT: Always call super.context(); when overriding this!
37          *
38          * This can be used in the main context to setup things that apply to all specs.
39          * Ideally at that point the dependencies should be prepared and the sut constructed.
40          *
41          * Any more specific setups should be done inside the current context class.
42          * Here we should setup things that are specific to the behavior we are testing.
43          *
44          */
45         protected function context() : void
46         {
47         }
49         /**
50          * After the context has been setup and the sut is thus prepared, we act on it.
51          * e.g. we invoke a method, set a property or cause a dependency (mock) to interact with it.
52          * The results of this action (normally it should be only one) will then be checked inside the test methods.
53          *
54          */
55         protected function because() : void
56         {
57         }
59         /**
60          *
61          * This is a helper that allows to execute a piece of code that will most likely cause an error.
62          * After invoking it, we can examine the caughtError property to validate that the expected type
63          * of error was thrown and that the message contained what we expected.
64          *
65          * This approach is more flexible than putting a meta-tag for the expected error on the test method.
66          *
67          * @param func
68          * the function that will cause the error
69          *
70          */
71         protected function catchError(func : Function) : void
72         {
73             try
74             {
75                 func();
76                 caughtError = null;
77             }
78             catch (e : Error)
79             {
80                 caughtError = e;
81             }
82         }
83     }
84 }

As you can see the [Before] method, which is invoked before each test (spec), invokes the context() followed by the because(), consequently setting up the system under test and its dependencies and then acting on it.
We will override these methods in order to specify the contexts and actions.

The “the” method is there to “extend” our objects with “should” methods. It returns a SpecificationExtensions object and injects the value we are trying to check.

Here is the constructor and one of the methods inside the SpecificationExtensions class:

 1 public function SpecificationExtensions(actual : Object) : void
 2 {
 3     _actual = actual;
 4 }
 6 private var _actual : Object;
 8 public function shouldEqual(expected : Object) : SpecificationExtensions
 9 {
10     assertThat(_actual, equalTo(expected));
11     return this;
12 }

As we can see, calling the(value).shouldEqual(1); is only syntactic sugar for assertThat(value, equalTo(1));.
It reads much nicer though and speeds up coding due to the intellisense that pops up and allows us to choose the appropriate should method.

It is also possible to add these methods to the Object.prototype and that way allowing value.shouldEqual(1); , but of course there will no intellisense support in that case.

Since I am such a code assist junkie that makes it a no go for me.

Here is a little taste of the convenience:

In case you are wondering why it returns itself, it is to allowto code multiple assertions in a fluent style (this is very rare as ideally there should be only one assertion per specification).

Just for kicks, it would allow me to do this:

1 the(_sut.salary)
2     .shouldNotEqual(1)
3     .shouldNotEqual(2);

The Employee tests revisited

For now we have to part with the convenience of having all our tests for one class inside one file.

This is due to the limitation/rule of the Flex compiler that only allows one public class per ActionScript file and the fact that FlexUnit will not be able to find any tests contained in private classes.

In the next part I will show how to work around this.

For now we want to stick to the rules though in order to enjoy all the benefits of the integrated FlexUnit4, including the automated creation of a test runner.

As a starts we have the main context inside the EmployeeSpecs that does what the [Before] setup() method did in the previous example:

 1 package
 2 {
 3     import;
 4     import bddseparate.fakes.BankAccountMock;
 5     import specutils.base.SpecificationsBase;
 7     public class EmployeeSpecs extends SpecificationsBase
 8     {
 9         protected var _bankAccount_Mock : BankAccountMock;
10         protected var _sut : Employee;
12         override protected function context() : void
13         {
14             _bankAccount_Mock = new BankAccountMock();
15             _sut = new Employee(_bankAccount_Mock);
16         }
17     }
18 }

Then we have the following two contexts along with more specific sub contexts:

  • the bank account is connected
    • the salary is 1 dollar
    • the salary is 2 dollars
  • the bank account is not connected

Since we can only have one context per class, we need to organize our packages/classes in the following way.


It reads nicely from top to bottom e.g. employee.when_bank_account_is_connected.and_salary_is_1_dollar_paying_him.should_update_the_bankaccount

The test results are also very informative. If any test fails, looking at them will give us very detailed information.


Despite all these details the individual test names are not as verbose as before (e.g. “should_update_the_bank_account”) since a lot of information is contained in the package and class names.

The major problem with this approach is obvious though – packages and files exploded right in our face.

Where there was one file containing all employee tests, we now have 7 and need 2 extra packages to get them organized.

Walking the specification path

For completeness sake I’ll explain how it works – if it is too confusing, skip to the next approach which is easier to look at and will make a lot of things clear.

As I said, the main context is set up inside the EmployeeSpecs and all classes containing specs either directly (e.g. or indirectly inherit from it.

Lets take our previous example (employee.when_bank_account_is_connected.and_salary_is_1_dollar_paying_him.should_update_the_bankaccount) and follow it all the way through.

Here is the class containing the actual specifications:

 1 package
 2 {
 4     public class and_salary_is_1_dollar_paying_him extends Ctx_BankAccount_is_connected
 5     {
 6         private const SALARY : Number = 1;
 8         override protected function context() : void
 9         {
10             // make sure we call the context setup of Ctx_BankAccount_is_connected first
11             super.context();
12             _sut.salary = SALARY;
13         }
15         override protected function because() : void
16         {
17   ;
18         }
20         [Test]
21         public function should_set_was_paid_to_true() : void
22         {
23             the(_sut.wasPaid).shouldBeTrue;
24         }
26         [Test]
27         public function should_update_the_bank_account() : void
28         {
29             the(_bankAccount_Mock.updateWithAmountWasCalled).shouldBeTrue;
30         }
32         [Test]
33         public function should_update_the_bankaccount_with_1_dollar() : void
34         {
35             the(_bankAccount_Mock.updateWithAmountWasCalledWith).shouldEqual(SALARY);
36         }
37     }
38 }

As we can see, after setting up the specific context and acting on the system under test via the because method, it makes sure that the three specifications are met.

Note, that it inherits from the Ctx_BankAccount_is_connected class and calls its context() method before further defining its own context.

Here is the Ctx_BankAccount_is_connected class:

 1 package
 2 {
 3     import;
 5     public class Ctx_BankAccount_is_connected extends EmployeeSpecs
 6     {
 7         override protected function context() : void
 8         {
 9             // Make sure we build up onto the main context
10             super.context();
11             _bankAccount_Mock.isConnected = true;
12         }
13     }
14 }

As you can see it extends from the EmployeeSpecs class and now it should be clear how the context is created from the most general one inside the EmploySpecs and gets more and more specific as we walk up the inheritance chain until we arrive at our actual specifications.



  • ability to convey lots of information without verbose test names
  • contexts are built up incrementally and are centralized which makes for easier maintenance
  • specific/general contexts clearly communicate what is needed for individual/all specifications
  • actions and assertions are clearly separated into because() and [Test] methods
  • specifications are easy to read as they are one liners
  • also integrates fully with the integrated FlexUnit framework and thus there is no need to create custom test runners


  • file/package explosion
  • harder to understand and follow for people not familiar with the concept

In the next post I will explain how to avoid the packages/files explosion and will enter mockito into the picture.

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BDD with FlexUnit the traditional TDD way

Implementing tests the traditional TDD way

Source code for this approach is available at here.

We are now ready to look at the tests that we need for the project created in the previous post.

First of all we have to decide what we will be testing.

In this case I wanted to make ensure two things:

  1. that the Employee keeps track of its own status correctly (was he paid, fired?)
  2. that the Employee interacts correctly with the bank account
  3. that the Employer interacts correctly with the Employee

Note that at this point I am not worried about the functionality of the bank account as this will be implemented later.

The test project

I don’t believe in including test code inside my production code projects, so lets create a separate Flex library project for our tests.

In it we include a fakes package and a tests package.

The fakes package will contain the necessary mocks and stubs.

Inside the tests package we mirror the exact package structure of the project we are testing in order to easily find the classes and their related tests.

For example the is inside the package and so we put the inside our test project inside the the package.

A short excursion into fakes

For a more detailed introduction please read the mock Wikipedia page.

I will just mention some core points.

  • Mocks vs. Stubs
    • mocks help decide if a test will pass by having things verified, while stubs just stub out properties or method return values
    • as a general rule if a fake is not used in  a verification it is a stub, otherwise it is a mock
    • adhering to strict naming conventions makes it easier to see how a fake object is used in the tests
  • fakes and top down development
    • fakes help in developing our application test driven and top down
    • in our example, I can test the interactions of the Employee with the bank account without having implemented the latter. All I need is its interface and a mock that implements it. This way I can flesh out, what it needs to be able to do, before starting with the actual implementation. That way I avoid implementing behaviors that will not be needed after all. The design will also be improved because I see how it a class will be used while I am creating it.
  • fakes, dependency injection and interfaces
    • it is good practice to create an interface for every dependency and inject it as an interface (instead of as a concrete class) into the dependent class either via the constructor or its properties
    • while this is just good design, it makes testing much easier as it allows replacing the dependencies with fakes while testing the dependent class

As I said, his is a very brief look at the advantages of using fakes. For further reading consult the books in the suggested readings or the above mentioned wiki page.

The BankAccount Mock

Here is the code of the BankAccount interface inside the Accounting project:

package accounting.interfaces

	public interface IBankAccount
		function updateWithAmount(amount : Number) : void;

		function get isConnected() : Boolean;

The mock implements the interface, but has no real functionality:

package traditional.fakes
	import accounting.interfaces.IBankAccount;

	 * This class is just keeping track of what is done to it.
	 * It will be injected instead of the real thing and afterwards I can check if the System under Test
	 * interacted with it in the desired way.
	 * e.g. did it tell the BankAccount to update with the correct amount.
	 * @author tlorenz
	public class BankAccountMock implements IBankAccount

		public var updateWithAmountWasCalled : Boolean;
		public var updateWithAmountWasCalledWith : Number;
		private var _isConnected : Boolean;

		public function updateWithAmount(amount : Number) : void
			updateWithAmountWasCalled = true;
			updateWithAmountWasCalledWith = amount;

		public function get isConnected() : Boolean
			return _isConnected;

		public function set isConnected(value : Boolean) : void
			_isConnected = value;

Notice, that we added a setter for the isConnected property (not required by the interface), in order control the state of the bank account in our tests.

The Employee tests

Make sure to read the comments inside the following snippet, to get an idea of how it works and why we end up with these long test names.

	import accounting.interfaces.IEmployee;
	import org.flexunit.assertThat;
	import org.flexunit.asserts.*;
	import org.hamcrest.object.equalTo;
	import traditional.fakes.BankAccountMock;

	 * @author tlorenz
	 * quoting from this nice tutorial (with comments added):
	 * •	[Before] - Replaces the setup() method in FlexUnit 1 and allow using multiple methods. Supports async, timeout, order and ui attributes.
	 * 					- is executed before each test
	 * •	[After] - Replaces the teardown() method in FlexUnit 1 and allow using multiple methods. Supports async, timeout, order and ui attributes
	 * 					- is executed after each test
	 * 					- good unit tests should not need to undo anything after a test
	 * •	[BeforeClass] - allow running methods before test class. Supports order attribute.
	 * 					- is executed once before all tests
	 * •	[AfterClass] - allow running methods after test class. Supports order attribute.
	 * 					- is executed once after all tests
	 * 					- good unit tests should not need to undo anything after a test
	public class EmployeeTests

		// This will be injected instead of a real BankAccount and allows verification of interaction.
		private var _bankAccount_Mock : BankAccountMock;

		// _sut is System Under Test (what I am testing - in this case Employee)
		// this naming convention is taken from the in depth book: "xUnit Test Patterns: Refactoring Test Code"
		private var _sut : IEmployee;

		public function setup() : void
			_bankAccount_Mock = new BankAccountMock();
			_sut = new Employee(_bankAccount_Mock);

		public function Initially_WasPaidIsFalse() : void

		public function Initially_WasFiredIsFalse() : void

		public function Initially_SalaryIsZero() : void
			assertThat(_sut.salary, equalTo(0));

		public function WhenToldThatHeIsFired_WasFiredIsTrue() : void


		// The following Testnames follow the pattern suggested by Roy Osherove in his "The Art of UnitTesting"
		// [Test]
		// public function Situation_Action_Result
		// As can be seen further down, this can result in very verbose testnames when the situation is a little complex

		public function BankAccountIsConnected_Paying_SetsWasPaidToTrue() : void
			_bankAccount_Mock.isConnected = true;;


		public function BankAccountIsConnected_Paying_UpdatesBankAccount() : void
			_bankAccount_Mock.isConnected = true;;


		public function BankAccountIsNotConnected_Paying_SetsWasPaidToFalse() : void
			_bankAccount_Mock.isConnected = false;;


		public function BankAccountIsNotConnected_Paying_DoesNotUpdateBankAccount() : void
			_bankAccount_Mock.isConnected = false;;


		public function SalaryIs1DollarAndBankAccountIsConnected_Paying_UpdatesBankAccountWith1Dollar() : void
			const SALARY : Number = 1;

			_sut.salary = SALARY;

			_bankAccount_Mock.isConnected = true;;

			assertThat(_bankAccount_Mock.updateWithAmountWasCalledWith, equalTo(SALARY));

		public function SalaryIs2DollarsAndBankAccountIsConnected_Paying_UpdatesBankAccountWith2Dollars() : void
			const SALARY : Number = 2;

			_sut.salary = SALARY;

			_bankAccount_Mock.isConnected = true;;

			assertThat(_bankAccount_Mock.updateWithAmountWasCalledWith, equalTo(SALARY));

Running these tests produces the following output:

The long test names are necessary for us to know right away what went wrong when a  test fails. Ideally we don’t even want to look at the test code, but go right to the production code to fix the problem.

Obviously a test name like “testingWasFired” won’t accomplish that goal. Instead we include the Context (Situation), what we did (Act/Because) and what result we were expecting. In BDD terms the test name takes on this format: Context_Because_ExpectedResult. This maps to the TDD naming: Situtaion_Action_ExpectedResult.

From looking at some of the resulting test names like:


or as found inside the Employer tests (part of the downloadable source code):


we can see that this could become a problem once we are dealing with more complex contexts and/or actions.

Note: the first 4 tests names deviate from this pattern, as there is either no context to be setup and/or nothing is done to the system under test.

Lets look closer at one of the Employee tests to show the naming convention in an example:

		public function BankAccountIsConnected_Paying_SetsWasPaidToTrue() : void
			_bankAccount_Mock.isConnected = true;;


The test name has the three parts which correspond to a line of code each:

  • Context:                              BankAccountIsConnected     _bankAccount_Mock.isConnected = true;
  • Because:                             Paying                                   ;
  • Expected Result:             SetsWasPaidToTrue                  assertTrue(_sut.wasPaid);

Test maintenance

There is one more very important disadvantage to the described approach.

Once  the functionality of the system under test grows, we need to prepare more things in order to run our tests. The problem is though, that preparations needed by test2 may not be necessary for test1 and vice versa.

As a result if we setup everything that is needed by either test inside the [Before] method, it becomes hard to see which preparation each test actually needs, which makes troubleshooting a failed test that much harder.

If , on the other hand, we put these individual preparations inside the test methods itself, we will pay for it later, when the class under test changes.

For example lets say 10 tests setup the system under test  by calling a method on it that takes currently one parameter. If we now change it to take another (non-optional) parameter, we have to change the invocation in all these 10 tests.

This can become a huge problem and make changes to our code a lengthy process, which is of course not desirable in an agile environment.

Another way around these is to factor out the commonalities into separate methods e.g. prepareInvocatorTests(). At this point though it becomes difficult again to understand each test because in order to do so, we have to navigate to an extra method.

On the other hand, there are clear advantages to writing our tests in this way, as I will mention inside the summary section which will close the discussion of each of the three different approaches I am presenting.



  • easier to understand for people new to BDD/ TDD than the approaches shown next
  • fully integrates with FlexUnit and doesn’t require the creation of custom test runners
  • all tests for a class are contained inside one ActionScript file


  • verbose test names can become a problem
  • when contexts become more complex and need to be different for each test, they either become less readable or a maintenance nightmare

We’ll take a first stab at solving these issues in the next part.

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BDD with FlexUnit and mockito Introduction


Coming from a .Net background with strong emphasis  on best practices, one of my first missions when learning Flex, was to figure out how I could implement Behavior Driven Development  in this environment.

I tried a lot of different approaches and will show three of them in the following posts.

I will not explain what is meant by BDD – there are numerous blogs out there and a good starting point is this wikipedia article.

At this point a simple comparison to TDD (Test Driven Development) shall suffice:

  • Arrange in TDD corresponds to a Scenario/Context in BDD and is usually expressed inside a “Context”, “EstablishContext” or a “Given” codeblock
  • Act in TDD corresponds to an action done to the system under test and is expressed in BDD inside a “Because” or “When” codeblock
  • Assertions in TDD correspond to “should” methods in BDD like shouldEqual, shouldBeTrue etc.

The details of this correlation will become clear in the examples.

Choosing a testing framework

Although there are numerous Flex testing frameworks out there, none of them lend themselves particularly well to BDD.


I gave  fluxunit – modeled after Rspec , a testing framework for Ruby – a drive.

It’s architecture would be very BDD enabling, but at this point it is still missing a lot of needed aspects.

For example it presents all test results as panels inside the browser window, marking the failed ones as red, which would require the developer to go hunt for the failures by scrolling through all of them.

That and the fact that no stack traces of the failures are given, make it not mature enough to be used in a serious project at this point.

Unfortunately it seems to be a dead, since it wasn’t updated for over a year.

Other testing frameworks are not offering anything very different to what is offered by FlexUnit4 which additionally has the following advantages:

  • it is fully integrated into Adobe’s FlashBuilder and allows running the tests and inspecting the results inside the IDE
  • it is supported by Adobe and will most likely be evolved in the future
  • a lot of frameworks related to testing (e.g. the mocking framework mockito) integrate with FlexUnit
  • there is a lot of good documentation out there like this “getting up and running” tutorial

FlexUnit4 is not designed to be used as a BDD framework though and a few hurdles will need to be overcome.

What we’ll be testing

The source code for this application is available here.

To get started, I implemented a sample application  following the traditional TDD style as explained in part 2.

The application I created has 3 components – an employer, an employee and a bank account:

  • BankAccount
    • is either connected or not
    • can be updated
  • Employee
    • can get fired
    • can get paid only if the bank account is connected
    • will show if he did good work or not
  • Employer
    • handles the Employee
    • evaluates the Employee and fires him if he didn’t do any good work
    • should only  pay the Employee when his salary is greater zero, he wasn’t paid before and was not fired either

Road map

I will show three different ways to test the above mentioned classes.

  1. The traditional way – TDD, using manually created mocks.
  2. BDD in a way that fully integrates with the FlexUnit4 framework and FlashBuilder and thus can use the automatically created test runner, but requires a lot of classes. We will use manually created mocks here as well.
  3. BDD in a way that requires us to create a custom test runner, but only two classes for our tests. We will use mockito to supply our mocks. This is in my opinion the most efficient way in order to get things done.
  4. A look at using mockito in a way that seamlessly integrates with the approach described above.

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