cookies and code

At the August Adogo meeting, I presented on the new features coming in FlexUnit4 and mock-as3. During the presentation, I showed the following sample (which has been updated) of how a FlexUnit 4 test using a customer runner for mock-as3 would work. Please keep in mind the example is a bit contrive but exemplifies the configuration options for the runner.

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package us.adogo.mock
{
   import com.anywebcam.mock.Mockery;
 
   import org.flexunit.Assert;
   import org.flexunit.assertThat;
   import org.hamcrest.core.not;
   import org.hamcrest.object.equalTo;
   import org.hamcrest.object.hasProperty;
   import org.hamcrest.object.nullValue;
 
   [RunWith("com.anywebcam.mock.runner.MockAs3TestRunner")]
   public class ExampleUsingMockAs3Runner {
      public var mockery : Mockery;
 
      [Mock]
      public var user : User;
 
      [Mock(inject="false")]
      public var account : Account;
 
      private var controller : UserController; 
 
      [Before]
      public function setUp() : void {
         account = mockery.nice(Account, ["1234567890"]) as Account;
         this.controller = new UserController(); 
      }
 
      [Test]
      public function testAddUserWithUsernameAndPasswordOnly() : void {
         //setup mock
         mockery.mock(user).method("save").calls(function () : void {
            user.id = 1;
         }).once;
 
         //populate object properties as you usually would
         user.username = "bobdobbs";
         user.password = "mysecret";
 
         //execute my controller method being tested
         controller.addUser(user);
 
         //test that the currentUsers went up by one and that its id is 1
         assertThat(controller.currentUsers.length, equalTo(1));
         assertThat(controller.currentUsers.getItemAt(0).id, equalTo(1));
         assertThat(controller.currentUsers.getItemAt(0).username, equalTo("bobdobbs"));
         assertThat(controller.currentUsers.getItemAt(0).password, equalTo("mysecret"));
      }
 
      [Test]
      public function testValidateUserAccount() : void {
         //setup mock
         mockery.mock(account).method("isValid").withArgs(User).returns(true).once;
 
         //execute my controller method being tested
         var expected : Boolean = controller.validateUser(new User(), account);
 
         //test that the account is valid
         Assert.assertTrue(expected);
      }
 
      [Test(verify="false")]
      public function testDefaultUserSize() : void {
         assertThat(controller, hasProperty("currentUsers"));
         assertThat(controller.currentUsers, not(nullValue()));
         assertThat(controller.currentUsers.length, equalTo(0));
      }
   }
}

This evening I updated the Adogo SVN with a working version of this runner and thought I’d detail its initial implementation.

• To use the runner place the metadata [RunWith("com.anywebcam.mock.runner.MockAs3TestRunner")] on the test class’ declaration.
• Once annotated with metadata, the test class will not run unless a public variable, or setter, is available of type com.anywebcam.mock.Mockery. This will allow the runner to inject a Mockery object and prepare() the mockery to produce mock objects. Using and preparing a mockery is a new requirement for mock-as3 if you’re utilizing type-safe mocks due to the asmock integration.
• Any public variable, or setter, annotated with the metadata [Mock] will have a type safe version of it injected automatically prior to the execution of each test method. By default a nice mock will be used, but if you specify the “type” attribute (e.g. – [Mock(type="strict")]) as “strict” then a strict mock will then be used. The difference between nice and strict mocks, is the equivalent of the “ignoreMissing” constructor argument on com.anywebcam.mock.Mock being set to true, or false, respectively.
• If the [Mock] metadata is used on a class with a constructor requiring arguments, whether they are optional or …rest, the runner cannot automatically inject the mock due to a limitation in its underlying dependency on the asmock library. If you need a mock object instance using constructor arguments, set the attribute “inject” as false (e.g. – [Mock(inject="false")]. Doing so will tell the runner that you’re going to use the mock-as3 framework directly to create the mock. The ideal place to do this in your test is within the [Before] methods defined for the test class. By going through all this hoopla, you get automatic mock prepration and verification, just as with the automatically injected mock objects.
• After the execution of each test method, the runner will automatically call verify() on each object variable/property marked with the [Mock] metadata. If you’d like to disable verify() from being called on all mocks for a test method, simply add the attribute “verify”, with a value of false, to your [Test] metadata (e.g. – [Test(verify="false")]). This can be helpful if you want the runner to inject the mockery and all of your mocks, but you would like to specify which mocks are verified for the test.
• Currently this runner requires FlexUnit 4 Beta 2 and a custom build of mock-as3 to work as stated. You can find SWCs for each in the Adogo August project linked above.

What’s important to note, is that this runner is more restrictive than using the mock-as3 framework directly, so it may not suite your needs. I based this runner off of concepts I saw in the JMock runner for JUnit 4, the @Mock annotation found in Mockito for Java, and my own testing practices. If anyone finds time to play with it and you find any gremlins, let me know. In speaking with Drew, it looks like this may make it into the next release of mock-as3 along with a couple of other cool features, so I hope people find it helpful.

UPDATE: Drew has been kind enough to deploy this FU4 test runner to the mock-as3 SVN repository under the class name com.anywebcam.mock.runner.MockRunner. Please use this copy for future reference. Please also note this version will only work with FlexUnit4 Beta2 and earlier. FlexUnit4 RC1 has changed the implementation for test runners and this code will need to be updated.

Well I gave my hastely assembled and zero practiced version of a FlexUnit4 and mock-as3 presentation last night at the Adogo and I only caught a few people snoozing, so that is a +1 in my book. Unit testing can be extremely dry for most people, but building tools to make me more productive always holds my interest so that’s how I’ll explain my enthusiasm. Thanks to Drew Bourne and Michael Labriola for the help with the presentation. I blubbered through most of the points on their APIs and definitely mispoke on a few instances, but as long as the recording doesn’t get too much traffic we should be fine. Thanks as well to Russ, Vincent, Brian, and Greg for keeping me company after the meeting over a few beers while I waited for my wife’s flight to get in.

I’ve published the source and recording for anyone who is interested.

I’m going to be presenting at this Monday’s (08/03/2009) August Adogo meeting after a few month hiatus due to the new baby. I’ll be running through the new features in FlexUnit4 and some work I’m doing with Drew on mock-as3. Afterwards, we are going to have a group discussion on “Uses for RIAs” where we’ll try to talk about where RIAs are applicable and how they can be abused. If you’re interested in testing in Flex or developer discussion, come by and see the latest and greatest coming out of the community. We have a sponsor for the meeting, so there will be food.

I hope you can make it out.

Over the last few weeks, while preparing my presentation for FlexCamp Miami a bit more, I have run into quite the plethora of tools to help developers test their Flex applications. I thought I’d take some time to break down what types of tools are available to help us out.

Unit Testing Frameworks

• fluint – http://code.google.com/p/fluint/
• flexunit – http://opensource.adobe.com/wiki/display/flexunit/FlexUnit
• funit – http://blog.funit.org/
• asunit – http://www.asunit.org/

Mock Object Frameworks

• mock-as3 – http://code.google.com/p/mock-as3/
• asmock – http://asmock.sourceforge.net/
• mock4as – http://code.google.com/p/mock4as/

Other useful libraries

• hamcrest-as3 – Assertion library – http://github.com/drewbourne/hamcrest-as3/tree/master
• asx – Extension methods for AS3 base types – http://github.com/drewbourne/asx/tree/master
• loom – Byte-code weaving framework for AS3 – http://code.google.com/p/loom-as3/

My favorite combination right now is fluint, mock-as3, hamcrest-as3, and asx. Although asmock supports type-safe mocking, I’m not a big fan of the record/replay model; for now I’m gonna stick with mock-as3 and wait until it supports type-safe mocks (<cough>loom integration<cough>. I’ve also found a major need for stubs when classes in my integration tests depend on HTTPService and RemoteObject. Sometimes its tough to mock out these classes because of complex interfaces these objects maintain, so I’ve come up with a pretty cool way of handling this. Hopefully I can publish the sample code here in the next few days for those who are interested.

I’d also like to give props to a couple people I’ve been working with in the community: Michael Labriola, Max Porges and Drew Bourne. Mike is working tirelessly to bring a more modern unit testing framework, a la JUnit 4 + more, to Flex via fluint along with tons of other initiatives. mock-as3, hamcrest-as3, and asx are all APIs that Drew has written; hamcrest-as3 alone is going to be providing some really powerful integration for assertions in unit testing frameworks. Max has been chipping away at the ABC spec with loom for months now, and once finished it’s going to provide a lot of great potential for more mature tooling/libraries in the Flex world … think AOP. Each of these code-bases are intuitive, easy to use, and were some of the biggest pieces missing from the Flex testing world until now. Keep up the great work guys! With any luck, we may soon have the tools we need to be as productive as developers in almost every other language out there.

So in my search for mock object libraries, I continue to run into frustration with explicit typing in ActionScript 3. I did some searching and found a really great mock object library called mock-as3. It’s an expectation based library, in its early stages, but surprisingly featured and intuitive. Here are some usage examples from the author.

I’ve been writing code in ActionScript using explicit types, like most everyone I know who uses AS3, so mock-as3 out of the box won’t meet my needs. If I wanted to begin using interface classes and stubbing out my mocks (as mentioned in the examples) I could, but I won’t; the author even comments that it is extremely tedious to do and doesn’t necessarily advocate it. He hopes to have features in future versions of the library available to handle this but for now they are not available. In general, implementing interfaces for all classes that I’d like to mock is something I don’t agree with in any language. I’m a believer that refactoring your code will make a use case for the use of a programmatic interface over time; there are explicit cases where they are useful, but in the case of mocking, I’m not a big fan.

In any case, I did some thinking and wondered if there was a way to convert an object to a different type at runtime. I figured it’d take some bytecode manipulation, but I’m new to the game, so others much have thought about this already I assumed. Sure enough, I found an implementation by Darron Schall called ObjectTranslator which will convert an object’s type at run-time. I ran through some basic examples and everything worked as expected, so I thought, why not try to convert Mock, which is the class used to mock an object, to the class type passed in at instantiation? The implementation of ObjectTranslator just switches a byte for the new class type and directly copies the bytes of the object into a new byte stream. Worth a shot right?

In mock-as3′s implementation Mock is a subclass of everyone’s favorite class, Proxy. I did a basic test creating an expectation with the same name as the method in my class I wanted to mock and then used ObjectTranslator to convert the mock’s type. I then passed the typed mock to something to consume it and test to see if my expectations return value was given. Below is a the code I wrote:

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var mock : Mock = new Mock(new MyClass());
trace(describeType(mock));
 
mock.method("method1").returns("PASS!");
trace(mock.method1());
 
var newMock : MyClass = ObjectTranslator.objectToInstance(mock, MyClass);
trace(describeType(newMock));
 
var typedUsage : UsageClass = new UsageClass(newMock);
trace(typedUsage.method1() == "PASS!");

Everything works except the final call to trace() which shows false because the value being returned is “FAIL!”, which is the default value for the method in the class declaration. I thought, well maybe I can add functionality to Mock where on each call to method() or property() I will create a property on the mock with the same name of the property passed in and point it to callProperty or getProperty from Proxy. Mock is declared dynamic after all. I gave it a whirl but no luck, I’m guessing there is something special done with Proxy that when I used ObjectTranslator, didn’t come over. There were also some properties used by Mock that didn’t come over because they were not part of the new type, specifically expectations. Since mock-as3 uses its internal reference to expectations I was hoping I would get this for free, but it didn’t work out from what I can tell. Without a way to eval() the code necessary to create a method signature matching the existing signature in the class declaration, I’m pretty much stumped.

If anyone has any suggestions, I’m all for it, but I kinda threw up my hands and called it a day. The more I play with ActionScript 3, the more it feels like the Flex community is going to have to produce things equivalent to CGLib to do anything flexible with ActionScript3 that is still type-safe (e.g. – mocks, AOP, etc). It sounds like from a thread on FlexCoders that the community really wants a Proxy#newProxyInstance method, so hopefully this will make Proxy a little more useful. I’m not sure, however, if they want to be able to instantiate Proxy at run-time or be able to instantiate a formal target property from Proxy of the target’s type. I’m hoping for the latter, but I’m still new to AS3, so who knows. Back to stubs …