Update developer docs (valkey-io#2354)

node/DEVELOPER.md

@@ -128,6 +128,13 @@ To run tests, use the following command:
 npm test
 ```
 
+To execute a specific test, include the [`testNamePattern`](https://jestjs.io/docs/cli#--testnamepatternregex) option. For example:
+
+```bash
+npm run test -- --testNamePattern="transaction"
+```
+
+IT suite starts the server for testing - standalone and cluster installation using `cluster_manager` script.
 To run the integration tests with existing servers, run the following command:
 
 ```bash

python/DEVELOPER.md

@@ -147,6 +147,13 @@ To execute a specific test, include the `-k <test_name>` option. For example:
 pytest --asyncio-mode=auto -k test_socket_set_and_get
 ```
 
+IT suite starts the server for testing - standalone and cluster installation using `cluster_manager` script.
+If you want IT to use already started servers, use the following command line from `python/python` dir:
+
+```bash
+pytest --asyncio-mode=auto --cluster-endpoints=localhost:7000 --standalone-endpoints=localhost:6379
+```
+
 ### Submodules
 
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