EDT:IDE Test Server
The IDE Test Server is a Jetty-based server which allows users to test their applications on the fly with virtually no configuration, and zero deployment, required. An example is that you can invoke a service directly from its source project without having to deploy the service, or even set up a server for it to run on.
The user never has to define, configure, or start the test server. A test server is created for each project in the workspace, as needed. The test server is started the first time it's requested. If the user wishes to restart the server, for example a classpath change was made, then the user only needs to terminate the server and it will be started back up automatically on the next access. This server lives under the covers, and the only place you see it running is the Debug view. Since each project has its own test server, each instance is a separate Java process in this view. This allows you to kill/restart a single project's server without affecting the other running servers.
The following sections are for EDT developers; they explain how you can get a server instance and how you can actually extend the server itself.
Using the test server in your application
If you want to invoke the test server from your application, you will need to depend on the org.eclipse.edt.ide.testserver project. Since each project has its own test server you will need to know the project for which you want a test server. Once you know this, you should use org.eclipse.edt.ide.testserver.TestServerManager.getInstance().getServerConfiguration(IProject project, boolean debug) to get a org.eclipse.edt.ide.testserver.TestServerConfiguration. You can also directly instantiate TestServerConfiguration but this makes sure there is just one server per project instead of spawning multiple instances.
Once you have a TestServerConfiguration you can invoke its start(IProgressMonitor monitor, boolean waitForServerToStart) method to start it up. If the server is already started this method will immediately return. An example of invoking this code can be found in org.eclipse.edt.ide.rui.server.EvServer of the org.eclipse.edt.ide.rui plug-in.
Once you have a running server, the TestServerConfiguration can tell you the port on which it is running, which is information you'll need to know when you want to load some URL on the server.
Extending the test server
If you are adding support for some new technology in EDT, you will probably need to also extend the test server. The test server resides in project org.eclipse.edt.ide.testserver and is a barebones Jetty server. The main support that ships with EDT is actually provided as an extension that you can use as a reference. The extension provided in EDT is the ability to invoke REST and dedicated services, as well as support JNDI data sources in these services.
There are two main pieces you will need to implement: code running inside the IDE that sets up any additional arguments, classpath additions, etc; and code running inside the test server process that handles configurations such as registering a new servlet.
(The reference implementation is located in plug-in org.eclipse.edt.ide.deployment.services; see plugin.xml as well as package org.eclipse.edt.ide.deployment.services.internal.testserver)
The kick this off you will need to add an extension point for org.eclipse.edt.ide.testserver.testServerExtension in your plugin.xml that references a class extending org.eclipse.edt.ide.testserver.AbstractTestServerContribution. Take a look at the source for this class to see the current available API. Every method is optional and you only need to override the methods that are needed in your application (for example you might not have any additional classpath entries to contribue). To see this class in action, refer to org.eclipse.edt.ide.deployment.services.internal.testserver.ServicesContribution.
Note: This class is a singleton for the workspace; the current TestServerConfiguration is passed to each method so that you can maintain state if you need to (see ServicesContribution for how this can be done).
If you need to contribute code running from within the server, you must write a class that extends org.eclipse.edt.ide.testserver.AbstractConfigurator. In order to register this class with the server, you must specify it in AbstractTestServerConfiguration.getConfiguratorClassNames() otherwise the test server will not be instructed to instantiate your class. Be sure that you add the appropriate classpath entry in AbstractTestServerContribution.getClasspathAdditions() so that the class can be loaded!