}
        with(getTargetServices()) {
            val scriptHandler = get(ScriptHandlerFactory::class.java).create(scriptSource, targetScope)
            val pluginManager = get(PluginManagerInternal::class.java)
            val pluginApplicator = get(PluginRequestApplicator::class.java)
            pluginApplicator.applyPlugins(PluginRequests.of(pluginRequests), scriptHandler, pluginManager, targetScope)
        }
        targetScope.lock()

import org.gradle.api.initialization.ConfigurableIncludedBuild
import org.gradle.api.initialization.ProjectDescriptor
import org.gradle.api.initialization.Settings
import org.gradle.api.initialization.dsl.ScriptHandler
import org.gradle.api.initialization.resolve.DependencyResolutionManagement
import org.gradle.api.invocation.Gradle
import org.gradle.api.plugins.ExtensionContainer
import org.gradle.api.plugins.ObjectConfigurationAction

        group = "Plugin development"
        outputFile = project.layout.buildDirectory.file("reports/plugins/validation-report-for-$idWithoutDots.txt")

        val scriptHandler = project.buildscript as ScriptHandlerInternal
        val scriptClassPath = scriptHandler.scriptClassPath.asFiles
        classpath = project.files(scriptClassPath)

        val archiveOperations = findArchiveOperations(project)

        val sourceHash = TestHashCodes.hashCodeFrom(42)

        val scriptHandler = mock<ScriptHandlerInternal> {
            on { repositories } doReturn mock<RepositoryHandler>()
        }

        val scriptHost = scriptHostWith(
            target = mock<Settings>(),
            scriptHandler = scriptHandler
        )
        val programHost = safeMockProgramHost {

        ConfigureUtil.configureByMap(options, action);
        action.execute();
    }

    @Override
    public ScriptHandler getBuildscript() {
        return scriptServices.get(ScriptHandler.class);
    }

    @Override
    public void buildscript(Closure configureClosure) {
        ConfigureUtil.configure(configureClosure, getBuildscript());
    }

        _ * serviceRegistry.get(ClassLoaderScopeRegistry) >> Mock(ClassLoaderScopeRegistry)
        _ * serviceRegistry.get(FileResolver) >> Mock(FileResolver)
        _ * serviceRegistry.get(ScriptHandler) >> Mock(ScriptHandler)
        _ * serviceRegistry.get(TaskExecutionGraphInternal) >> Mock(TaskExecutionGraphInternal)
        _ * serviceRegistry.get(TaskContainerInternal) >> Mock(TaskContainerInternal)

import org.gradle.api.artifacts.dsl.DependencyHandler;
import org.gradle.api.artifacts.dsl.DependencyLockingHandler;
import org.gradle.api.artifacts.dsl.RepositoryHandler;
import org.gradle.api.initialization.dsl.ScriptHandler;
import org.gradle.api.internal.artifacts.DependencyResolutionServices;
import org.gradle.api.internal.artifacts.JavaEcosystemSupport;
import org.gradle.api.internal.artifacts.configurations.ConfigurationRolesForMigration;

     *
     * A null target indicates that no plugin requests should be resolved but only the setup of the given
     * {@link ClassLoaderScope}.
     */
    void applyPlugins(PluginRequests requests, ScriptHandlerInternal scriptHandler, @Nullable PluginManagerInternal target, ClassLoaderScope classLoaderScope);

    @EventScope(Scope.Build.class)
    @StatefulListener
    interface PluginApplicationListener {

    }
}


private
fun buildInitScriptModel(initScript: File, rootProject: ProjectInternal): NonProjectScriptModel {
    val gradle = rootProject.gradle

    val (scriptHandler, scriptClassPath) = compilationClassPathForScriptPluginOf(
        target = gradle,
        scriptFile = initScript,
        baseScope = gradle.classLoaderScope,

====

The closure passed to the `initscript()` method configures a link:{javadocPath}/org/gradle/api/initialization/dsl/ScriptHandler.html[ScriptHandler] instance.
You declare the init script classpath by adding dependencies to the `classpath` configuration.

This is the same way you declare, for example, the Java compilation classpath.