Run jUnit tests on a remote machine / JVM.
- uses java serialization and HTTP for communication
- load classes from local machine (remote class loading)
- embeddable and integratable server, no separate port needed
- minimal footprint server (3 public classes), no dependencies except nanohttpd which consists of a single class
First, add a maven dependency to the server 
Then create a server class
public class Server {
public static void main(String... args) {
new CodeRunnerStandaloneServer().startAndWait();
}
}
and a unit test using the RemoteTestRunner
@RunWith(RemoteTestRunner.class)
public class SimpleJUnitTest {
@Test
public void simple() {
assertEquals("foo", "foo");
}
}
Now, start the server and run the unit test. The test will be executed in the server JVM.
The server is a generic server to inject an run code in a JVM. It is implemented by the CodeRunnerRequestHandler which handles requests and returns responses in the form of byte arrays.
This allows you to integrate the server in any way you need. You can easily implement a Servlet or integrate it with your web framework.
In addition, there is the CodeRunnerStandaloneServer, which starts a nanohttpd server, listening on a specific port (4578 by default)
To run a test remotely, simply annotate it with the @RunWith(RemoteTestRunner.class). You can set the test runner to be used using the @Remote(runnerClass=...) and the URL to connect to (where the server is listening) using the @Remote(endpoint=...) annotation.
The specified endpoint can be overridden by the junit.remote.endpoint system property. If set to - or if the server cannot be reached, the tests are executed locally. This makes it easy to use the unit tests from maven, since no server start/stop has to be managed.
Remote JUnit uses an architecture with 3 Layers.
The CodeRunnerClient simply sends a RequestHandlingServerCode instance along with a fixed set of class definitions to the server, where the code will be executed.
The ClassLoadingCodeRunnerClient uses the CodeRunnerClient to start a some RequestHandlingServerCode and establish a bi-directional message channel with it. A MessageHandlingServerCode is sent along and loaded using a custom class loader. Using the message channel, missing class definitions are requested by the custom class loader from the client. In addition, custom messages can be exchanged with the MessageHandlingServerCode.
Finally, using this infrastructure the RemoteTestRunner executes unit tests on the server, forwarding the JUnit test run notifications back to the client.
See the javadoc for CodeRunnerClient, ClassLoadingCodeRunnerClient and RemoteTestRunner for details.