If the nested type is a managed type (Gradle can generate its implementation), you can define a nested property with:
```
interface NestedType {
    Property<String> getSomeProperty()
}
class Example {
    @Nested
    NestedType getNestedProperty()
}
```
Otherwise, if the nested type requires an implementation class, you'll need to manage the lifecycle of it:
```
interface NestedType {

        this.requirement = requirement;
    }

    public String getImplementation() {
        return implementation;
    }

    public void setImplementation(String implementation) {
        this.implementation = implementation;
    }

    public String getSince() {
        return since;
    }

    public void setSince(String since) {

dependencies {
    implementation("gradlebuild:basics")

    implementation(projects.dependencyModules)
    implementation(projects.jvm)
    implementation(projects.kotlinDslSharedRuntime)

    implementation(kotlin("gradle-plugin"))
    implementation(kotlin("sam-with-receiver"))
    implementation("org.ow2.asm:asm")
    implementation("com.thoughtworks.qdox:qdox")

    implementation(projects.basics)
    implementation(projects.moduleIdentity)

    implementation("net.ltgt.gradle:gradle-errorprone-plugin:4.1.0")
    implementation("net.ltgt.gradle:gradle-nullaway-plugin:2.2.0")


    implementation("org.gradle.kotlin.kotlin-dsl:org.gradle.kotlin.kotlin-dsl.gradle.plugin:$expectedKotlinDslPluginsVersion")

}

application {
  mainClass.set("okhttp3.survey.RunSurveyKt")
}

dependencies {
  implementation(projects.okhttp)
  implementation(projects.okhttpCoroutines)
  implementation(libs.conscrypt.openjdk)

  implementation(libs.retrofit)
  implementation(libs.converter.moshi)
  implementation(libs.squareup.moshi)
  implementation(libs.squareup.moshi.kotlin)

  ksp(libs.squareup.moshi.compiler)
}

tasks.compileJava {

        }
        verifyNoInteractions(mockDir);
    }

    /**
     * Edge: passing a null directory object. Interface allows null; implementation decides.
     */
    @Test
    @DisplayName("null directory is handled by implementation")
    void handlesNullDirectory() throws Exception {
        SmbFilenameFilter filter = (dir, name) -> dir == null;

/**
 * Tests for the NdrObject abstract class.
 * This test uses a concrete implementation to verify the abstract contract.
 */
@ExtendWith(MockitoExtension.class)
class NdrObjectTest {

    @Mock
    private NdrBuffer mockBuffer;

    private ConcreteNdrObject ndrObject;

    // A concrete implementation of NdrObject for testing purposes.
    private static class ConcreteNdrObject extends NdrObject {

          .build();

  /**
   * type → implementation. Inherently mutable interfaces and abstract classes are mapped to their
   * default implementations and are "new"d upon get().
   */
  private static final ConcurrentMap<Class<?>, Class<?>> implementations = Maps.newConcurrentMap();

  private static <T> void setImplementation(Class<T> type, Class<? extends T> implementation) {

 * this case, you should override {@code add(Object)} as well, either providing your own
 * implementation, or delegating to the provided {@code standardAdd} method.
 *
 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
 * default} methods. Instead, it inherits their default implementations. When those implementations
 * invoke methods, they invoke methods on the {@code ForwardingMultiset}.
 *

 * override {@code putAll} as well, either providing your own implementation, or delegating to the
 * provided {@code standardPutAll} method.
 *
 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
 * default} methods. Instead, it inherits their default implementations. When those implementations
 * invoke methods, they invoke methods on the {@code ForwardingNavigableMap}.
 *