import org.gradle.test.fixtures.maven.MavenModule

class ModuleSpec {
    private final String groupId
    private final String artifactId
    private final Map<String, ModuleVersionSpec> versions = [:].withDefault { new ModuleVersionSpec(groupId, artifactId, it) }

    private List<InteractionExpectation> metadataExpectations = []

    ModuleSpec(String group, String name) {
        groupId = group
        artifactId = name

class GroupSpec {
    private final String groupId
    final Map<String, ModuleSpec> modules = [:].withDefault { new ModuleSpec(groupId, it) }

    GroupSpec(String name) {
        groupId = name
    }

    void module(String name, @DelegatesTo(value = ModuleSpec, strategy = Closure.DELEGATE_ONLY) Closure<Void> moduleSpec) {
        moduleSpec.delegate = modules[name]
        moduleSpec.resolveStrategy = Closure.DELEGATE_ONLY
        moduleSpec()
    }

- Introduce `OS` field in the PodSpec...