diff --git a/test/e2e/extensions/test-extension/extension.ts b/test/e2e/extensions/test-extension/extension.ts
index ea962efbdd84..ea4a1f896ce6 100644
--- a/test/e2e/extensions/test-extension/extension.ts
+++ b/test/e2e/extensions/test-extension/extension.ts
@@ -2,6 +2,7 @@ import * as vscode from "vscode"
 
 export function activate(context: vscode.ExtensionContext) {
   vscode.window.showInformationMessage("test extension loaded")
+  // Test extension
   context.subscriptions.push(
     vscode.commands.registerCommand("codeServerTest.proxyUri", () => {
       if (process.env.VSCODE_PROXY_URI) {
@@ -11,4 +12,20 @@ export function activate(context: vscode.ExtensionContext) {
       }
     }),
   )
+
+  // asExternalUri extension
+  context.subscriptions.push(
+    vscode.commands.registerCommand("codeServerTest.asExternalUri", async () => {
+      const input = await vscode.window.showInputBox({
+        prompt: "URL to pass through to asExternalUri",
+      })
+
+      if (input) {
+        const output = await vscode.env.asExternalUri(vscode.Uri.parse(input))
+        vscode.window.showInformationMessage(`input: ${input} output: ${output}`)
+      } else {
+        vscode.window.showErrorMessage(`Failed to run test case. No input provided.`)
+      }
+    }),
+  )
 }
diff --git a/test/e2e/extensions/test-extension/package.json b/test/e2e/extensions/test-extension/package.json
index 8aca8815ac9f..77482689f4c4 100644
--- a/test/e2e/extensions/test-extension/package.json
+++ b/test/e2e/extensions/test-extension/package.json
@@ -17,6 +17,11 @@
         "command": "codeServerTest.proxyUri",
         "title": "Get proxy URI",
         "category": "code-server"
+      },
+      {
+        "command": "codeServerTest.asExternalUri",
+        "title": "asExternalUri test",
+        "category": "code-server"
       }
     ]
   },