feat(testkit): add SettingsScript.Builder and withSettingsScript.

src/functionalTest/groovy/com/autonomousapps/AbstractProject.groovy

@@ -71,7 +71,9 @@ abstract class AbstractProject extends AbstractGradleProject {
     return super.newGradleProjectBuilder(dslKind)
       .withRootProject { r ->
         r.gradleProperties += additionalProperties
-        r.settingsScript.plugins = new com.autonomousapps.kit.gradle.Plugins(plugins)
+        r.withSettingsScript { s ->
+          s.plugins(plugins)
+        }
       }
   }
 }

src/functionalTest/groovy/com/autonomousapps/android/projects/AbstractAndroidProject.groovy

@@ -85,7 +85,9 @@ abstract class AbstractAndroidProject extends AbstractProject {
     return newSettingsProjectBuilder(dslKind, withKotlin)
       .withRootProject { root ->
         root.gradleProperties += GradleProperties.minimalAndroidProperties()
-        root.settingsScript.buildscript = BuildscriptBlock.defaultAndroidBuildscriptBlock(agpVersion)
+        root.withSettingsScript { s ->
+          s.buildscript = BuildscriptBlock.defaultAndroidBuildscriptBlock(agpVersion)
+        }
       }
   }
 }

testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/RootProject.kt

@@ -35,9 +35,23 @@ public class RootProject(
     public var variant: String? = null
     public val files: MutableList<File> = mutableListOf()
 
-    // sub-builders
+    /*
+     * sub-builders
+     */
+
+    private var settingsScriptBuilder: SettingsScript.Builder? = null
     private var buildScriptBuilder: BuildScript.Builder? = null
 
+    public fun withSettingsScript(block: SettingsScript.Builder.() -> Unit) {
+      val builder = settingsScriptBuilder ?: SettingsScript.Builder()
+      settingsScript = with(builder) {
+        block(this)
+        // store for later building-upon
+        settingsScriptBuilder = this
+        build()
+      }
+    }
+
     public fun withBuildScript(block: BuildScript.Builder.() -> Unit) {
       val builder = buildScriptBuilder ?: defaultBuildScriptBuilder()
       buildScript = with(builder) {

testkit/gradle-testkit-support/src/main/kotlin/com/autonomousapps/kit/gradle/SettingsScript.kt

@@ -51,4 +51,36 @@ public class SettingsScript @JvmOverloads constructor(
     DslKind.GROOVY -> "include ':$subproject'"
     DslKind.KOTLIN -> "include(\":$subproject\")"
   }
+
+  public class Builder {
+    public var pluginManagement: PluginManagement = PluginManagement.DEFAULT
+    public var buildscript: BuildscriptBlock? = null
+    public var plugins: Plugins = Plugins.EMPTY
+    public var dependencyResolutionManagement: DependencyResolutionManagement? = DependencyResolutionManagement.DEFAULT
+    public var rootProjectName: String = "the-project"
+    public var subprojects: Set<String> = emptySet()
+
+    /** For random stuff, as-yet unmodeled. */
+    public var additions: String = ""
+
+    public fun plugins(vararg plugins: Plugin) {
+      this.plugins = Plugins(plugins.toMutableList())
+    }
+
+    public fun plugins(plugins: Iterable<Plugin>) {
+      this.plugins = Plugins(plugins.toMutableList())
+    }
+
+    public fun build(): SettingsScript {
+      return SettingsScript(
+        pluginManagement = pluginManagement,
+        buildscript = buildscript,
+        plugins = plugins,
+        dependencyResolutionManagement = dependencyResolutionManagement,
+        rootProjectName = rootProjectName,
+        subprojects = subprojects,
+        additions = additions,
+      )
+    }
+  }
 }