writeIndex();
        }

        public void onOutput(long classId, TestOutputEvent outputEvent) {
            onOutput(classId, 0, outputEvent);
        }

        public void onOutput(long classId, long testId, TestOutputEvent outputEvent) {
            boolean stdout = outputEvent.getDestination() == TestOutputEvent.Destination.StdOut;
            mark(classId, testId, stdout);

                writeOutputs(writer, classId, !options.outputPerTestCase, TestOutputEvent.Destination.StdOut);
                writer.endElement();
            }

            if (options.includeSystemErrLog) {
                writer.startElement("system-err");
                writeOutputs(writer, classId, !options.outputPerTestCase, TestOutputEvent.Destination.StdErr);
                writer.endElement();
            }

        TestDescriptor test2 = new DefaultTestDescriptor("1.1.2", "DogTest", "shouldLoiter");

        def woof = new DefaultTestOutputEvent(TestOutputEvent.Destination.StdOut, "woof woof!")
        def grrr = new DefaultTestOutputEvent(TestOutputEvent.Destination.StdErr, "grrr!")

        when:
        adapter.started(root, new TestStartEvent(1))
        adapter.started(suite, new TestStartEvent(1, '1'))

        private final Serializer<TestOutputEvent.Destination> destinationSerializer = new BaseSerializerFactory().getSerializerFor(TestOutputEvent.Destination.class);

        @Override
        public DefaultTestOutputEvent read(Decoder decoder) throws Exception {
            TestOutputEvent.Destination destination = destinationSerializer.read(decoder);

import spock.lang.Issue
import spock.lang.Specification

import static java.util.Arrays.asList
import static org.gradle.api.tasks.testing.TestOutputEvent.Destination.StdErr
import static org.gradle.api.tasks.testing.TestOutputEvent.Destination.StdOut
import static org.gradle.api.tasks.testing.TestResult.ResultType.FAILURE
import static org.gradle.api.tasks.testing.TestResult.ResultType.SUCCESS

import spock.lang.Issue
import spock.lang.Specification

import static java.util.Collections.emptyList
import static org.gradle.api.tasks.testing.TestOutputEvent.Destination.StdErr
import static org.gradle.api.tasks.testing.TestOutputEvent.Destination.StdOut
import static org.gradle.api.tasks.testing.TestResult.ResultType.FAILURE
import static org.gradle.api.tasks.testing.TestResult.ResultType.SKIPPED

     * passed to the closure as a parameter.
     *
     * <pre class='autoTested'>
     * apply plugin: 'java'
     *
     * test {
     *    onOutput { descriptor, event -&gt;
     *        if (event.destination == TestOutputEvent.Destination.StdErr) {

==== New Tooling API progress event

In Gradle 6.0, we introduced a new progress event (link:{javadocPath}/org/gradle/tooling/events/test/TestOutputEvent.html[org.gradle.tooling.events.test.TestOutputEvent]) to expose the output of test execution.
This new event breaks the convention of having a `StartEvent`-`FinishEvent` pair to express progress.
`TaskOutputEvent` is a simple `ProgressEvent`.