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High-level structure of Tradefed XML configuration

Tradefed's configurations follow an XML structure to describe the test to be run and the preparation/setup steps to be done.

In theory, everything can be defined in the XML for a single command. But in practice, it is more practical to have base template XML files and customize them with extra command line parameters.

Structure

<configuration description="<description of the configuration>">
    <!-- A build provider that takes local device information -->
    <build_provider class="com.android.tradefed.build.BootstrapBuildProvider" />

    <!-- Some target preparation, disabled by default -->
    <target_preparer class="com.android.tradefed.targetprep.PreloadedClassesPreparer">
        <option name="disable" value="true" />
    </target_preparer>

    <!-- One test running some unit tests -->
    <test class="com.android.tradefed.testtype.HostTest">
        <option name="class" value="com.android.tradefed.build.BuildInfoTest" />
    </test>

    <!-- [OPTIONAL] -->
    <logger class="com.android.tradefed.log.FileLogger">
        <option name="log-level" value="VERBOSE" />
        <option name="log-level-display" value="VERBOSE" />
    </logger>

    <!-- [OPTIONAL] -->
    <log_saver class="com.android.tradefed.result.FileSystemLogSaver" />

    <!-- As many reporters as we want -->
    <result_reporter class="com.android.tradefed.result.ConsoleResultReporter" />
    <result_reporter class="com.android.tradefed.result.suite.SuiteResultReporter" />
    <result_reporter class="com.android.tradefed.result.MetricsXMLResultReporter"/>
</configuration>

The overall Tradefed XML is delimited by <configuration> tags. Tradefed objects are defined in their own tags, for example: build_provider, target_preparer, test, etc. Their individual purposes are described in more detail in the Architecture section.

Each object has the Java class associated with the object defined in class= that is resolved at runtime; so as long as the JAR file containing the class is on the Tradefed Java classpath when running, it will be found and resolved.

Orders of Tradefed objects

The order of the different tags does not matter. For example, it makes no difference if build_provider is specified after target_preparer. The flow of the test invocation is enforced by the harness itself, so it will always call them in the right order.

The order of objects with the same tag does matter. For example, two target_preparer objects defined will be called in their order of definition in the XML. It is important to understand this as it can change the end state of the device setup. For example, flashing then installing an apk would not be the same as installing an apk and flashing since flashing would wipe the device.