class ThreadLocal {
 public:
  ThreadLocal() : key_(CreateKey()),
                  default_() {}
  explicit ThreadLocal(const T& value) : key_(CreateKey()),
                                         default_(value) {}

  ~ThreadLocal() {
    // Destroys the managed object for the current thread, if any.
    DeleteThreadLocalValue(pthread_getspecific(key_));

  // TestProperty object.
  TestProperty(const std::string& a_key, const std::string& a_value) :
    key_(a_key), value_(a_value) {
  }

  // Gets the user supplied key.
  const char* key() const {
    return key_.c_str();
  }

  // Gets the user supplied value.
  const char* value() const {
    return value_.c_str();
  }

        0 * _

        where:
        description        | key        | expectSideEffect
        "existing key"     | "some key" | 1
        "non-existing key" | "oops key" | 0
    }

    def "runs side effect when calling '#getter' on property's 'keySet'"() {
        def sideEffect1 = Mock(ValueSupplier.SideEffect)
        def sideEffect2 = Mock(ValueSupplier.SideEffect)

        then:
        failure.assertHasCause("Could not copy file '${file("src/two/two.a")}' to '${file("dest/two.a")}'.")
        failure.assertHasCause("Missing property (one) for Groovy template expansion. Defined keys [notused].")
    }

    def "useful help message when property cannot be expanded in filter chain"() {
        given:
        buildFile << """
            task copy (type: Copy) {