The Hedera Consensus Service (HCS) gRPC API is a public mirror node managed by Hedera for the testnet. It offers the ability to subscribe to HCS topics and receive messages for the topic subscribed. API docs for the mirror nodes can be found here:
{% page-ref page="../docs/mirror-node-api/" %}
{% hint style="info" %}
HCS Testnet Mirror Node Endpoints:
hcs.testnet.mirrornode.hedera.com:5600
REST API Testnet Root Endpoint:
https://testnet.mirrornode.hedera.com
{% endhint %}
If you don't have access to a Hedera testnet mirror node, you can check out the community hosted mirror node services for your testnet development below.