buildFile << '''
class UnmanagedThing {
    def getSomeProp() {
        return this
    }
    def conf(Closure cl) {
        cl.delegate = this
        cl.call()
    }
}

class MyPlugin extends RuleSource {
    @Model
    UnmanagedThing thing() { return new UnmanagedThing() }
}
apply plugin: MyPlugin

model {
    thing {
        conf {

        buildScript '''
            class UnmanagedThing {
              String value
            }
            class MyFile extends File {
              MyFile(String s) { super(s) }
            }

            @Managed
            interface ManagedThing {
                @Unmanaged
                UnmanagedThing getUnmanaged()
                void setUnmanaged(UnmanagedThing unmanaged)

                @Unmanaged

            extractionContext.child(ModelType.of(UnmanagedThing), "child")
            extractionContext.found(new ScalarValueSchema<CustomThing>(extractionContext.type))
        }
        1 * strategy.extract(_) >> { ModelSchemaExtractionContext extractionContext ->
            assert extractionContext.type == ModelType.of(UnmanagedThing)
            extractionContext.found(new ScalarValueSchema<UnmanagedThing>(extractionContext.type))
        }