Add test connection guide and related images for federated login

en/includes/guides/authentication/federated-login/index.md

@@ -72,6 +72,10 @@ You can register an external IdP in {{product_name}} by creating a connection. {
   </div>
 </div>
 
+## Test a connection
+
+{% include "../../fragments/manage-connection/test-connection.md" %}
+
 ## Configure JIT provisioning
 
 {% include "../../../guides/fragments/manage-connection/jit-provisioning.md" %}

en/includes/guides/fragments/manage-connection/test-connection.md

@@ -0,0 +1,42 @@
+<!-- markdownlint-disable-next-line -->
+
+You can verify that your connection is configured correctly by running a test against the federated identity provider. {{ product_name }} initiates an authentication request to the IdP and displays the result, letting you confirm that the connection works before using it in an application's login flow.
+
+To test a connection:
+
+1. On the {{ product_name }} Console, go to **Connections**.
+2. Select the **connection you want to test**.
+3. Click **Test Connection** on the connection page.
+
+    ![Test Connection button on a connection page]({{base_path}}/assets/img/guides/idp/test-connection/test-connection-button.png){: width="700" style="display: block; margin: 0; border: 0.3px solid lightgrey;"}
+
+4. {{ product_name }} redirects you to the federated identity provider's login page. Authenticate using a valid account from that IdP.
+5. After a successful authentication, you are redirected back to {{ product_name }}, and the test results are displayed.
+
+    ![Test results page showing a successful connection test]({{base_path}}/assets/img/guides/idp/test-connection/test-connection-results.png){: width="700" style="display: block; margin: 0; border: 0.3px solid lightgrey;"}
+
+The results page shows three tabs:
+
+<table>
+    <tr>
+        <th>Tab</th>
+        <th>Description</th>
+    </tr>
+    <tr>
+        <td>ID Token</td>
+        <td>Displays the decoded header and payload of the ID token returned by the federated IdP. Use this to verify that the token is well-formed and that expected claims such as <code>sub</code>, <code>iss</code>, and <code>aud</code> are present.</td>
+    </tr>
+    <tr>
+        <td>Claim Mappings</td>
+        <td>Lists the claims received from the IdP alongside the local claims they are mapped to in {{ product_name }}. Use this to confirm that claim mappings are resolving as expected.</td>
+    </tr>
+    <tr>
+        <td>Diagnosis</td>
+        <td>Provides a step-by-step diagnostic log of the connection test. Each entry shows the stage, outcome, and any error details, making it easier to pinpoint configuration issues.</td>
+    </tr>
+</table>
+
+!!! note
+    You can click **Rerun Test** at any time to run the connection test again without leaving the results page.
+
+If the test fails, review the **Diagnosis** tab for error details and verify the connection settings such as the client ID, client secret, and endpoint URLs.