type FakeCollectorManager … func (fkm *FakeCollectorManager) RegisterCollector(collector Collector) error { … } func (fkm *FakeCollectorManager) GetSpec() ([]v1.MetricSpec, error) { … } func (fkm *FakeCollectorManager) Collect(metric map[string][]v1.MetricVal) (time.Time, map[string][]v1.MetricVal, error) { … }