add link to Docker Hub for testing zkApps

docs/zkapps/how-to-test-a-zkapp.mdx

@@ -8,6 +8,7 @@ keywords:
   - Smart contract
   - Jest
   - Local blockchain
+  - Docker test
 ---
 
 :::info
@@ -18,10 +19,24 @@ zkApp programmability is not yet available on the Mina Mainnet. You can get star
 
 # How to Test a zkApp
 
-Writing automated tests for your smart contract is essential to ensure your code is well tested during development. All projects created using the Mina zkApp CLI include the [Jest](https://jestjs.io/) JavaScript testing framework. Although you can use any testing framework, the instructions in this document are supported for Jest.
+Writing automated tests for your smart contract is essential to ensure your code is well-tested during development. 
+
+## Test zkApps on a lightweight Mina local network
+
+A Docker image for Mina local networks provides a simple and efficient way to deploy and run lightweight Mina blockchain networks for testing zkApps. The `o1labs/mina-local-network` Docker image provides:
+
+- Genesis ledger with pre-funded accounts
+- Accounts manager service
+- Additional port served by reverse proxy to pass requests to the Mina daemon GraphQL endpoint so zkApps work without additional configuration
+- Single commands to launch a single node or multi node network
+
+Pull the [o1labs/mina-local-network]
+(https://hub.docker.com/r/o1labs/mina-local-network) image from Docker Hub.
 
 ## Writing tests for your smart contract
 
+All projects created using the Mina zkApp CLI include the [Jest](https://jestjs.io/) JavaScript testing framework. Although you can use any testing framework, the instructions in this document are supported for Jest.
+
 Use the Mina zkApp CLI to create tests for your smart contract.
 
 To scaffold a TypeScript file with a corresponding test file, run: