docs: standard test api link (#28309)

docs/docs/contributing/how_to/integrations/standard_tests.ipynb

@@ -191,6 +191,21 @@
     "</Tabs>"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Test suite information and troubleshooting\n",
+    "\n",
+    "For a full list of the standard test suites that are available, as well as\n",
+    "information on which tests are included and how to troubleshoot common issues,\n",
+    "see the [Standard Tests API Reference](https://python.langchain.com/api_reference/standard_tests/index.html).\n",
+    "\n",
+    "An increasing number of troubleshooting guides are being added to this documentation,\n",
+    "and if you're interested in contributing, feel free to add docstrings to tests in \n",
+    "[Github](https://github.com/langchain-ai/langchain/tree/master/libs/standard-tests/langchain_tests)!"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},