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Test Driven Development - Spring Application

I am developing a REST API. I have Jmeter tests already for the functional testing. I wanted to add unit tests and also want to follow test driven development(TDD) from now on to make any enhancement and add new functionality to my existing project (which is bound to grow very complex and does not have any unit tests in place).
After reading a lot about TDD I am little confused about whether I should be going for TDD. There are extreme outlooks for and against it.
I think I will follow TDD only to develop my service layer, which encompasses only business logic.
Any suggestions about my approach ?

TDD is more than that. It is not only a way for you to check if a system is externally working fine. TDD is also a means to accelerate development of your classes, even if they do not interact with other systems.
Think of a test as a response to the following questions:
Am I done developing this class?
Do the classes I already developed and tested still work fine after a change I've made?
How to represent requirements as source code?
An explanation about each question:
How do you know you are done writing a class? A test can tell you that by only showing a test successful message after your class does everything it was supposed to do.
You need test automation in order to test often.
Whenever you have a new requirement, write a new test that represents this requirement.

TDD is one of the best practices to follow as you would test before you develop. And you would know at each and every step during developing the application/service if you have broken any previous functionality.
You are at the right path and I would always encourage using TDD. If you are working on a project right from scratch then just go for it.
Since yours is an existing project it may be a headache at first till you cover unit test cases for all the existing functionality.
So the best approach is:
Write down all the unit test cases for existing functionality before you start development for new functionality.
While doing that you may come up with a lot of surprises and may end up re-factoring a lot of code. This will help you while developing future new functionality.
Now since your code looks much better you can start TDD for the new functionality.
Let me know if this helps. I have used TDD in many of my projects and I am comfortable with that.

Since you're using Spring, I'd suggest that the object to unit test should not be a web service. I'd make it an interface-based POJO. The behavior should not be affected by the choice to deploy as REST.
Marshaling and unmarshaling the HTTP request and response to objects for the POJO to consume can be separate.
This arrangement will have the added benefit of not requiring deployment to a container in order to test.

Automating complete testing of Java EE web application

I have a doubt. Say I have a web application which is big and relies on Java/Java EE (JSP/Servlets).
Every time before a drop we test each and every functionality on GUI so that everything is working properly. Previously it was easy but now as the number of modules has increased exponentially, manually testing each and every GUI with required functionality is no more a feasible option.
I am on lookout for tools in which I can write my entire test case say about 1000 and then just run it once before the drop and it will list down all the test cases that have failed.
The tool preferably must be free to download and use it.
I dont know whether using
Arquilian
or
JUnit
in this regard will help or not but automating testing before the drop is really needed..
Please guide.

Use Junit together with a mock framework i.e Mockito to test units (service methods)
Use Arquillian to test on an integration level ( how different services, modules work together )
Use a database testing tool (i.e dbunit) to test your database / persistence layer)
Use Selenium to test your frontend
Test as much as possible.
Use Jenkins and Sonar to track your build process and your quality of tests and code
You should always test your application on different level. There is not just one solution.
Use unit testing to test small pieces of your application and to make refactoring as easy as possible.
Use integration test to check your modules still work together as expected.
Use GUI testing to check if your customers can work with your software.
If its relevant, think about performance testing (i.e. jmeter )

Definitively Selenium. Couple it with maven cause you will probably need to package your project specifically for testing purpose. Moreover maven allow you to launch a container during the integration-test phase and to close it automatically at the end. You can also configure this as a nightly build on jenkins / hudson so you will be quicly notified of any regression.

Building a test suite in a large existing Java code base

I am working on a web application with an existing code base that has probably been around for 10 years, there are ~1000 class files and ~100,000 lines of code. The good news is that the code is organized well, business logic is separate from the controller domain, and there is a high level of reusability. The bad news is there is only the very beginnings of a test suite (JUnit); there's maybe 12 dozen tests at most.
The code is organized fairly typically for an enterprise Java project. There is a stuts-esque controller package, the model consists of almost purely data objects, there is a hibernate like database layer that is largely encapsulated within data access objects, and a handful of service packages that are simple, self contained, and logical. The end goal of building this test suite is to move towards a continuous integration development process.
How would you go about building a test suite for such an application?
What tools would you use to make the process simpler?
Any suggestions welcome. thanks!

Start by reading Working Effectively with Legacy Code (short version here). Next I would write a couple of end-to-end smoke tests to cover the most common use cases. Here are some ideas on how to approach it: http://simpleprogrammer.com/getting-up-to-bat-series/
Then when I need to change some part of the system, I would cover it with focused unit tests (refer to the aforementioned book) and then do the change. Little by little the system - or at least the parts which change the most often - would be better covered and working with it would become easier.

I would create a few integration tests. Since they toch a lot of code, you probably will get an error when you screw up bigtime.
I wouldn't 'build a testsuite' as such, but rather before changing some part define a testset for it, and then go about changing it.
I would suggest looking into a test coverage tool (I don't code Java, so no clue what tool the best is for Java). While it does not tell you when you've tested enough, it does tell you when you tested too little ;)
Good luck!

If the project isn't already maven-ized I would do that. Also be sure to use a mocking framework like mockito. Hudson is a nice CI tool that integrates nicely with maven.

It looks like you are going to be writing both unit and functional tests, so JUnit might not be the best fit for this. Have you considered TestNG? Since you only have very few tests right now, you have the option to pick what's best for the job.

Java/J2EE standard practices and design choices

I have a couple of design/architectural questions that always come up in our shop. I said "our", as opposed to "me" personally. Some of the decisions were made and made when J2EE was first introduced so there are some bad design choices and some good.
In a web environment, how do you work with filters. When should you use J2EE filters and when shouldn't you? Is it possible to have many filters, especially if you have too much logic in them. For example, there is a lot of logic in our authentication process. If you are this user, go to this site and if not go to another one. It is difficult to debug because one URL path could end up rendering different target pages.
Property resource bundle files for replacement values in JSP files: It seems that the consensus in the Java community is to use bundle files that contain labels and titles for a jsp parsing. I can see the benefit if you are doing development with many different languages and switching the label values based on locale. But what if you aren't working with multiple languages? Should every piece of static text in a JSP file or other template file really have to be put into a property file. Once again, we run into issues with debugging where text may not show up due to misspelling with property value keys or corrupt property files. Also, we have a process where graphic designers will send us html templates and then we convert them to jsp. It seems it more confusing to then remove the static text, add a key, add the key/value in a property file, etc.
E.g. A labels.properties file may contain the Username: label. That gets replaced by some key and rendered to the user.
Unit Testing for all J2EE development - we don't encourage unit testing. Some people do but I have never worked at shop that uses extensive unit testing. Once place did and then when crunch time hit, we stopped doing unit testing and then after a while the unit tests were useless and wouldn't ever compile. Most of the development I have done has been with servers, web application development, database connectivity. I see where unit testing can be cumbersome because you need an environment to unit test against. I think unit test manifestos encourage developers not to actually connect to external sources. But it seems like a major portion of the testing should be connecting to a database and running all of the code, not just a particular unit. So that is my question, for all types of development (like you see in CRUD oriented J2EE development) should we write unit tests in all cases? And if we don't write unit tests, what other developer testing mechanisms could we use?
Edited: Here are some good resources on some of these topics.
http://www.ibm.com/developerworks/java/library/j-diag1105.html

Redirection is a simpler way to handle different pages depending on role. The filter could be used simply for authentication, to get the User object and any associated Roles into the session.
As James Black said, if you had a central controller you could obviate the need to put this logic in the filters. To do this you'd map the central controller to all urls (or all non-static urls). Then the filter passes a User and Roles to the central controller which decides where to send the user. If the user tries to access a URL he doesn't have permission for, this controller can decide what to do about it.
Most major MVC web frameworks follow this pattern, so just check them out for a better understanding of this.
I agree with James here, too - you don't have to move everything there but it can make things simpler in the future. Personally, I think you often have to trade this one off in order to work efficiently with designers. I've often put the infrastructure and logic in to make it work but then littered my templates with static text while working with designers. Finally, went back and pulled all the static text out into the external files. Sure enough, found some spelling mistakes that way!
Testing - this is the big one. In my experience, a highly disciplined test-first approach can eliminate 90% of the stress in developing these apps. But unit tests are not quite enough.
I use three kinds of tests, as indicated by the Agile community:
acceptance/functional tests - customer defines these with each requirement and we don't ship til they all pass (look at FitNesse, Selenium, Mercury)
integration tests - ensure that the logic is correct and that issues don't come up across tiers or with realistic data (look at Cactus, DBUnit, Canoo WebTest)
unit tests - both defines the usage and expectations of a class and provides assurance that breaking changes will be caught quickly (look at JUnit, TestNG)
So you see that unit testing is really for the benefit of the developers... if there are five of us working on the project, not writing unit tests leads one of two things:
an explosion of necessary communication as developers try and figure out how to use (or how somebody broke) each other's classes
no communication and increased risk due to "silos" - areas where only one developer touches the code and in which the company is entirely reliant on that developer
Even if it's just me, it's too easy to forget why I put that little piece of special case logic in the class six months ago. Then I break my own code and have to figure out how... it's a big waste of time and does nothing to reduce my stress level! Also, if you force yourself to think through (and type) the test for each significant function in your class, and figure out how to isolate any external resources so you can pass in a mock version, your design improves immeasurably. So I tend to work test-first regardless.
Arguably the most useful, but least often done, is automated acceptance testing. This is what ensures that the developers have understood what the customer was asking for. Sometimes this is left to QA, and I think that's fine, but the ideal situation is one in which these are an integral part of the development process.
The way this works is: for each requirement the test plan is turned into a script which is added to the test suite. Then you watch it fail. Then you write code to make it pass. Thus, if a coder is working on changes and is ready to check in, they have to do a clean build and run all the acceptance tests. If any fail, fix before you can check in.
"Continuous integration" is simply the process of automating this step - when anyone checks code in, a separate server checks out the code and runs all the tests. If any are broken it spams the last developer to check in until they are fixed.
I once consulted with a team that had a single tester. This guy was working through the test plans manually, all day long. When a change took place, however minor, he would have to start over. I built them a spreadsheet indicating that there were over 16 million possible paths through just a single screen, and they ponied up the $10k for Mercury Test Director in a hurry! Now he makes spreadsheets and automates the test plans that use them, so they have pretty thorough regression testing without ever-increasing QA time demands.
Once you've begun automating tests at every layer of your app (especially if you work test-first) a remarkable thing happens. Worry disappears!
So, no, it's not necessary. But if you find yourself worrying about technical debt, about the big deployment this weekend, or about whether you're going to break things while trying to quickly change to meet the suddenly-urgent customer requirements, you may want to more deeply investigate test-first development.

Filters are useful to help move logic such as is the user authenticated, to properly handle this, since you don't want this logic in every page.
Since you don't have a central controller it sounds like your filters are serving this function, which is fine, but, as you mentioned, it does make debugging harder.
This is where unit tests can come in handy, as you can test different situations, with each filter individually, then with all the filters in a chain, outside of your container, to ensure it works properly.
Unit testing does require discipline, but, if the rule is that nothing goes to QA without a unit test then it may help, and there are many tools to help generate tests so you just have to write the test. Before you debug, write or update the unit test, and show that the unit test is failing, so the problem is duplicated.
This will ensure that that error won't return, and that you fixed it, and you have updated a unit test.
For resource bundles. If you are certain you will never support another language, then as you refactor you can remove the need for the bundles, but, I think it is easier to make spelling/grammar corrections if the text is actually in one place.

Filters in general are expected to perform smaller units of functionality and filter-chaining would be used to apply the filters as needed. In your case, maybe a refactoring can help to move out some of the logic to additional filters and the redirecting logic can be somewhat centralized through a controller to be easier to debug and understand.
Resource bundles are necessary to maintain flexibility, but if you know absolutely that the site is going to be used in a single locale, then you might skip it. Maybe you can move some of the work in maintaining the bundles to the designers i.e let them have access to the resource bundles, so that you get the HTML with the keys in place.
Unit testing is much easier to implement at the beginning of a project as opposed to building it into a existing product. For existing software, you may still implement unit tests for the new features. However, it requires a certain amount of insistence from team leads and the team needs to buy into the necessity of having unit tests. Code review for unit tests helps and a decision on what parts of the code need to be absolutely covered can help developers. Tools/plugins like Coverlipse can indicate the unit testing coverage, but they tend to look at every possible code path, some of which may be trivial.
At one of my earlier projects, unit tests were just compulsory and unit tests would be automatically kicked off after each check-in. However, this was not Test-driven development, as the tests were mostly written after the small chunks of code were written. TDD can result in developers writing code to just work with the unit tests and as a result, developers can lose the big picture of the component they are developing.

In a web environment, how do you work with filters. When should you use J2EE filters and when shouldn't you?
Filters are meant to steer/modify/intercept the actual requests/responses/sessions. For example: setting the request encoding, determining the logged-in user, wrapping/replacing the request or response, determining which servlet it should forward the request to, and so on.
To control the actual user input (parameters) and output (the results and the destination) and to execute actual business logic, you should use a servlet.
Property resource bundle files for replacement values in JSP files.
If you don't do i18n, just don't use them. But if you ever grow and the customer/users want i18n, then you'll be happy that you're already prepared. And not only that, it also simplifies the use of a CMS to edit the content by just using the java.util.Properties API.
Unit Testing for all J2EE development
JUnit can take care about it. You can also consider to "officially" do user tests only. Create several use cases and test it.

How can I improve my junit tests

Right my junit tests look like a long story:
I create 4 users
I delete 1 user
I try to login with the deleted user and make sure it fails
I login with one of the 3 remaining user and verify I can login
I send a message from one user to the other and verify that it appears in the outbox of the sender and in the inbox of the receiver.
I delete the message
...
...
Advantages:
The tests are quite effective (are very good at detecting bugs) and are very stable, becuase they only use the API, if I refactor the code then the tests are refactored too. As I don't use "dirty tricks" such as saving and reloading the db in a given state, my tests are oblivious to schema changes and implementation changes.
Disadvantages:
The tests are getting difficult to maintain, any change in a test affects other tests. The tests run 8-9 min which is great for continuous integration but is a bit frustrating for developers. Tests cannot be run isolated, the best you can do is to stop after the test you are interested in has run - but you absolutely must run all the tests that come before.
How would you go about improving my tests?

First, understand the tests you have are integration tests (probably access external systems and hit a wide range of classes). Unit tests should be a lot more specific, which is a challenge on an already built system. The main issue achieving that is usually the way the code is structured:
i.e. class tightly coupled to external systems (or to other classes that are). To be able to do so you need to build the classes in such a way that you can actually avoid hitting external systems during the unit tests.
Update 1: Read the following, and consider that the resulting design will allow you to actually test the encryption logic without hitting files/databases - http://www.lostechies.com/blogs/gabrielschenker/archive/2009/01/30/the-dependency-inversion-principle.aspx (not in java, but ilustrates the issue very well) ... also note that you can do a really focused integration tests for the readers/writers, instead of having to test it all together.
I suggest:
Gradually include real unit tests on your system. You can do this when doing changes and developing new features, refactoring appropriately.
When doing the previous, include focused integration tests where appropriate. Make sure you are able to run the unit tests separated from the integration tests.
Consider your tests are close to testing the system as a whole, thus are different from automated acceptance tests only in that they operate on the border of the API. Given this think about factors related to the importance of the API for the product (like if it will be used externally), and whether you have good coverage with automated acceptance tests. This can help you understand what is the value of having these on your system, and also why they naturally take so long. Take a decision on whether you will be testing the system as a whole on the interface level, or both the interface+api level.
Update 2: Based on other answers, I want to clear something regarding doing TDD. Lets say you have to check whether some given logic sends an email, logs the info on a file, saves data on the database, and calls a web service (not all at once I know, but you start adding tests for each of those). On each test you don't want to hit the external systems, what you really want to test is if the logic will make the calls to those systems that you are expecting it to do. So when you write a test that checks that an email is sent when you create an user, what you test is if the logic calls the dependency that does that. Notice that you can write these tests and the related logic, without actually having to implement the code that sends the email (and then having to access the external system to know what was sent ...). This will help you focus on the task at hand and help you get a decoupled system. It will also make it simple to test what is being sent to those systems.

unit tests should - ideally - be independent, and able to run in any order. So, I would suggest that you:
break up your tests to be independent
consider using an in-memory database as the backend for your tests
consider wrapping each test or suite in a transaction that is rolled back at the end
profile the unit tests to see where the time is going, and concentrate on that
if it takes 8 minutes to create a few users and send a few messages, the performance problem may not be in the tests, rather this may be a symptom of performance problems with the system itself - only your profiler knows for sure!
[caveat: i do NOT consider these kinds of tests to be 'integration tests', though i may be in the minority; i consider these kinds of tests to be unit tests of features, a la TDD]

Now you are testing many things in one method (a violation of One Assertion Per Test). This is a bad thing, because when any of those things changes, the whole test fails. This leads it to not being immediately obvious why a test failed and what needs to be fixed. Also when you intentionally change the behaviour of the system, you need to change more tests to correspond the changed behaviour (i.e. the tests are fragile).
To know what kind of tests are good, it helps to read more on BDD: http://dannorth.net/introducing-bdd http://techblog.daveastels.com/2005/07/05/a-new-look-at-test-driven-development/ http://jonkruger.com/blog/2008/07/25/why-behavior-driven-development-is-good/
To improve the test that you mentioned, I would split it into the following three test classes with these context and test method names:
Creating user accounts
Before a user is created
the user does not exist
When a user is created
the user exists
When a user is deleted
the user does not exist anymore
Logging in
When a user exists
the user can login with the right password
the user can not login with a wrong password
When a user does not exist
the user can not login
Sending messages
When a user sends a message
the message appears in the sender's outbox
the message appears in the reciever's inbox
the message does not appear in any other message boxes
When a message is deleted
the message does not anymore exist
You also need to improve the speed of the tests. You should have a unit test suite with good coverage, which can run in a couple of seconds. If it takes longer than 10-20 seconds to run the tests, then you will hesitate to run them after every change, and you lose some of quick feedback that running the tests gives you. (If it talks to the database, it's not a unit test, but a system or integration test, which have their uses, but are not fast enough to be executed continually.) You need to break the dependencies of the classes under test by mocking or stubbing them. Also from your description it appears that your tests are not isolated, but instead the tests depend on the side-effects caused by previous tests - this is a no-no. Good tests are FIRST.

Reduce dependencies between tests. This can be done by using Mocks. Martin Fowler speaks about it in Mocks aren't stubs, especially why mocking reduces dependencies between tests.

You can use JExample, an extension of JUnit that allows test methods to have return values that are reused by other tests. JExample tests run with the normal JUnit plugin in Eclipse, and also work side by side with normal JUnit tests. Thus migration should be no problem. JExample is used as follows
#RunWith(JExample.class)
public class MyTest {
#Test
public Object a() {
return new Object();
}
#Test
#Given("#a")
public Object b(Object object) {
// do something with object
return object;
}
#Test
#Given("#b")
public void c(Object object) {
// do some more things with object
}
}
Disclaimer, I am among the JExample developers.

If you use TestNG you can annotate tests in a variety of ways. For example, you can annotate your tests above as long-running. Then you can configure your automated-build/continuous integration server to run these, but the standard "interactive" developer build would not (unless they explicitly choose to).
This approach depends on developers checking into your continuous build on a regular basis, so that the tests do get run!
Some tests will inevitably take a long time to run. The comments in this thread re. performance are all valid. However if your tests do take a long time, the pragmatic solution is to run them but not let their time-consuming nature impact the developers to the point that they avoid running them.
Note: you can do something similar with JUnit by (say) naming tests in different fashions and getting your continuous build to run a particular subset of test classes.

By testing stories like you describe, you have very brittle tests. If only one tiny bit of functionality is changing, your whole test might be messed up. Then you will likely to change all tests, which are affected by that change.
In fact the tests you are describing are more like functional tests or component tests than unit tests. So you are using a unit testing framework (junit) for non-unit tests. In my point of view there is nothing wrong to use a unit testing framework to do non-unit tests, if (and only if) you are aware of it.
So there are following options:
Choose another testing framework which supports a "story telling"-style of testing much better, like other user already have suggested. You have to evaluate and find a suitable testing framework.
Make your tests more “unit test”-like. Therefore you will need to break up your tests and maybe change your current production code. Why? Because unit testing aims on testing small units of code (unit testing purists suggest only one class at once). By doing this your unit tests become more independent. If you change the behavior of one class, you just need to change a relatively small amount of unit test code. This makes your unit test more robust. During that process you might see that your current code does not support unit testing very well -- mostly because of dependencies between classes. This is the reason that you will also need to modify your production code.
If you are in a project and running out of time, both options might not help you any further. Then you will have to live with those tests, but you can try to ease your pain:
Remove code duplication in your tests: Like in production code eliminate code duplication and put the code into helper methods or helper classes. If something changes, you might only need to change the helper method or class. This way you will converge to the next suggestion.
Add another layer of indirection to your tests: Produce helper methods and helper classes which operate on a higher level of abstraction. They should act as API for your tests. These helpers are calling you production code. Your story tests should only call those helpers. If something changes, you need to change only one place in your API and don't need to touch all your tests.
Example signatures for your API:
createUserAndDelete(string[] usersForCreation, string[] userForDeletion);
logonWithUser(string user);
sendAndCheckMessageBoxes(string fromUser, string toUser);
For general unit testing I suggest to have a look into XUnit Test Patterns from Gerard Meszaros.
For breaking dependencies in your production tests have a look into Working Effectively with Legacy Code from Michael Feathers

In addition to the above, pick up a good book on TDD (I can recommend "TDD and Acceptance TDD for Java Developers"). Even though it will approach from a TDD point of view there is alot of helpful information about writing the right kind of unit tests.
Find someone who has alot of knowledge in the area and use them to figure out how you can improve your tests.
Join a mailing list to ask questions and just read the traffic coming through. The JUnit list at yahoo (something like groups.yahoo.com/junit). Some of the movers and shakers in the JUnit world are on that list and actively participate.
Get a list of the golden rules of unit tests and stick them on your (and others) cubicle wall, something like:
Thou shalt never access an external system
Thou shalt only test the code under test
Thou shalt only test one thing at once
etc.

Since everyone else is talking about structure I'll pick different points. This sounds like a good opportunity to profile the code to find bottleknecks and to run it through code coverage to see if you are missing anything (given the time it takes to run it the results could be interesting).
I personally use the Netbeans profiler, but there are ones in other IDEs and stand alone ones as well.
For code coverage I use Cobertura, but EMMA works too (EMMA had an annoyance that Cobertura didn't have... I forget what it was and it may not be an issue anymore). Those two are free, there are paid ones as well that are nice.