JUnit @rule for running Dropwizard integration test. Ps! This is just a proof of concept. There are probably some landminds lying around waiting to go off, especially around lifecycle management and static state

DropwizardTestServer.java

package com.developerb.dropwizard;

import com.yammer.dropwizard.AbstractService;
import com.yammer.dropwizard.Service;
import com.yammer.dropwizard.cli.Command;
import com.yammer.dropwizard.config.Configuration;
import org.junit.rules.TestRule;
import org.junit.runner.Description;
import org.junit.runners.model.Statement;

import java.lang.reflect.Method;
import java.net.URI;

/**
 * JUnit @Rule that'll start and stop a Dropwizard service around each test method.
 *
 * This class might be extended with factory methods for pre-configured http client
 * instance for both the main and the internal service endpoint.
 *
 * @author Kim A. Betti <[email protected]>
 */
public class DropwizardTestServer<C extends Configuration, S extends Service<C>> implements TestRule {

    private final Class<C> configurationClass;
    private final Class<S> serviceClass;
    private final String config;

    private TestableServerCommand<C> command;
    private S service;

    protected DropwizardTestServer(Class<C> configClass, Class<S> serviceClass, String config) {
        this.configurationClass = configClass;
        this.serviceClass = serviceClass;
        this.config = config;
    }

    public static <C extends Configuration, S extends Service<C>> DropwizardTestServer<C, S> testServer(
                        Class<C> configClass, Class<S> serviceClass, String config) {
        return new DropwizardTestServer<>(configClass, serviceClass, config);
    }

    @Override
    public Statement apply(Statement base, Description description) {
        return new DropwizardStatement(base);
    }

    public boolean isRunning() {
        return command.isRunning();
    }

    public S getService() {
        return service;
    }

    public URI getPublicRootUri() {
        return command.getRootUriForConnector("main");
    }

    public URI getInternalRootUri() {
        return command.getRootUriForConnector("internal");
    }

    private class DropwizardStatement extends Statement {

        private final Statement base;

        public DropwizardStatement(Statement base) {
            this.base = base;
        }

        @Override
        public void evaluate() throws Throwable {
            service = serviceClass.newInstance();
            registerTestCommand(service);

            try {
                service.run(new String[] { "test-server", config });
                base.evaluate();
            }
            finally {
                command.stop();
            }
        }

        /**
         * Register a custom command that'll allow us to register our test-server
         * startup logic that in turn will let us shut it down in a controlled fashion.
         *
         * I really don't like using reflection like this, but it's better then introducing
         * a new abstract class in the Service class hierarchy solely for testing purposes.
         */
        private void registerTestCommand(Service<C> service) throws Exception {
            command = new TestableServerCommand<>(configurationClass);

            Method method = AbstractService.class.getDeclaredMethod("addCommand", Command.class);
            method.setAccessible(true);
            method.invoke(service, command);
        }

    }

}

SampleIntegrationTest.java

package com.developerb.dropwizard;

import com.developerb.dropwizard.DropwizardTestServer;
import com.google.inject.Injector;
import Sample.server.SampleConfiguration;
import Sample.server.SampleService;
import org.apache.http.client.HttpClient;
import org.apache.http.client.ResponseHandler;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.BasicResponseHandler;
import org.junit.Rule;
import org.junit.Test;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;

import static com.developerb.dropwizard.DropwizardTestServer.testServer;
import static junit.framework.Assert.assertEquals;
import static junit.framework.Assert.assertTrue;

/**
 * @author Kim A. Betti <[email protected]>
 */
public class SampleIntegrationTest {

    @Rule
    public DropwizardTestServer<SampleConfiguration, SampleService> testServer
                       = testServer(SampleConfiguration.class, SampleService.class, "config.yml");

    @Test
    public void shouldBeRunning() {
        assertTrue("Server should be running", testServer.isRunning());
    }

    @Test
    public void weHaveAccessToPublicRootUri() throws URISyntaxException {
        URI expectedUri = new URI("http://localhost:8080");
        assertEquals(expectedUri, testServer.getPublicRootUri());
    }

    @Test
    public void weAlsoHaveAccessToInternalRootUri() throws URISyntaxException {
        URI expectedUri = new URI("http://localhost:8081");
        assertEquals(expectedUri, testServer.getInternalRootUri());
    }

    @Test
    public void playingPingPong() throws IOException {
        HttpClient httpClient = getHttpClientFromService();
        URI root = testServer.getInternalRootUri();

        String pingResponseBody = executeSimpleHttpGet(httpClient, root, "/ping");
        assertEquals("pong", pingResponseBody.trim());

        httpClient.getConnectionManager().shutdown();
    }

    private String executeSimpleHttpGet(HttpClient httpClient, URI root, String path) throws IOException {
        HttpGet initialFetch = new HttpGet(root.toString() + path);
        ResponseHandler<String> responseHandler = new BasicResponseHandler();
        return httpClient.execute(initialFetch, responseHandler);
    }

    private HttpClient getHttpClientFromService() {
        SampleService service = testServer.getService();
        Injector injector = service.getInjector();
        return injector.getInstance(HttpClient.class);
    }

}

TestableServerCommand.java

package com.developerb.dropwizard;

import com.yammer.dropwizard.AbstractService;
import com.yammer.dropwizard.cli.ConfiguredCommand;
import com.yammer.dropwizard.config.Configuration;
import com.yammer.dropwizard.config.Environment;
import com.yammer.dropwizard.config.HttpConfiguration;
import com.yammer.dropwizard.config.ServerFactory;
import com.yammer.dropwizard.logging.Log;
import org.apache.commons.cli.CommandLine;
import org.eclipse.jetty.server.Connector;
import org.eclipse.jetty.server.Server;

import javax.management.*;
import java.lang.management.ManagementFactory;
import java.net.URI;
import java.net.URISyntaxException;

import static com.google.common.base.Preconditions.checkArgument;

/**
 * Normally ServerCommand is in charge of starting the service, but that's not particularly
 * well suited for integration testing as it joins the current thread and keeps the Server
 * instance to itself.
 *
 * This implementation is based on the original ServerCommand, but in addition to being
 * stoppable it provides a few convenience methods for tests.
 *
 * @author Kim A. Betti <[email protected]>
 */
public class TestableServerCommand<T extends Configuration> extends ConfiguredCommand<T> {

    private final Log log = Log.forClass(TestableServerCommand.class);

    private final Class<T> configurationClass;

    private Server server;

    public TestableServerCommand(Class<T> configurationClass) {
        super("test-server", "Starts an HTTP test-server running the service");
        this.configurationClass = configurationClass;
    }

    @Override
    protected Class<T> getConfigurationClass() {
        return configurationClass;
    }

    @Override
    protected void run(AbstractService<T> service, T configuration, CommandLine params) throws Exception {
        server = initializeServer(service, configuration);

        try {
            server.start();
        }
        catch (Exception e) {
            log.error(e, "Unable to start test-server, shutting down");
            server.stop();
        }
    }

    public void stop() throws Exception {
        try {
            stopJetty();
        }
        finally {
            unRegisterLoggingMBean();
        }
    }

    /**
     * We won't be able to run more then a single test in the same JVM instance unless
     * we do some tidying and un-register a logging m-bean added by Dropwizard.
     */
    private void unRegisterLoggingMBean() throws Exception {
        MBeanServer server = ManagementFactory.getPlatformMBeanServer();
        ObjectName loggerObjectName = new ObjectName("com.yammer:type=Logging");
        if (server.isRegistered(loggerObjectName)) {
            server.unregisterMBean(loggerObjectName);
        }
    }

    private void stopJetty() throws Exception {
        if (server != null) {
            server.stop();
            checkArgument(server.isStopped());
        }
    }

    public boolean isRunning() {
        return server.isRunning();
    }

    public URI getRootUriForConnector(String connectorName) {
        try {
            Connector connector = getConnectorNamed(connectorName);
            String host = connector.getHost() != null ? connector.getHost() : "localhost";
            return new URI("http://" + host + ":" + connector.getPort());
        }
        catch (URISyntaxException e) {
            throw new IllegalStateException(e);
        }
    }

    private Connector getConnectorNamed(String name) {
        Connector[] connectors = server.getConnectors();
        for (Connector connector : connectors) {
            if (connector.getName().equals(name)) {
                return connector;
            }
        }

        throw new IllegalStateException("No connector named " + name);
    }

    private Server initializeServer(AbstractService<T> service, T configuration) throws Exception {
        Environment environment = getInitializedEnvironment(service, configuration);
        ServerFactory serverFactory = getServerFactory(service, configuration);

        return serverFactory.buildServer(environment);
    }

    private ServerFactory getServerFactory(AbstractService<T> service, T configuration) {
        HttpConfiguration httpConfig = configuration.getHttpConfiguration();
        return new ServerFactory(httpConfig, service.getName());
    }

    private Environment getInitializedEnvironment(AbstractService<T> service, T configuration) throws Exception {
        Environment environment = new Environment(configuration, service);
        service.initializeWithBundles(configuration, environment);
        return environment;
    }

}

Oh, I didn't realize that people had been commenting on this! Thanks for all the feedback!

Thanks for sharing this. If folks can settle for a class-level JUnit approach for integration testing, Dropwizard 0.6.2 seems to have quietly added a DropwizardServiceRule (see https://github.com/codahale/dropwizard/pull/307/files) for this purpose.

import com.yammer.dropwizard.testing.junit.DropwizardServiceRule;

...

@ClassRule
public static final DropwizardServiceRule<TestConfiguration> RULE = 
    new DropwizardServiceRule<TestConfiguration>(MyService.class, 
        Resources.getResource("my-service-config.yml").getPath());

...

@Test
    public void fooTest() {
        Client client = new Client();
        String root = String.format("http://localhost:%d/", RULE.getLocalPort());
        URI uri = UriBuilder.fromUri(root).path("/foo").build();
        WebResource rs = client.resource(uri);

...

API (without docs, unfortunately) appears to be here too:
http://dropwizard.codahale.com/maven/dropwizard-testing/apidocs/com/yammer/dropwizard/testing/junit/DropwizardServiceRule.html