test case for predicted output

.dotnet/tests/Chat/ChatTests.cs

@@ -870,4 +870,36 @@ public async Task ReasoningTokensWork()
         Assert.That(completion.Usage.OutputTokenDetails?.ReasoningTokenCount, Is.GreaterThan(0));
         Assert.That(completion.Usage.OutputTokenDetails?.ReasoningTokenCount, Is.LessThan(completion.Usage.OutputTokenCount));
     }
+
+    [Test]
+    public async Task PredictedOutputsWork()
+    {
+        ChatClient client = GetTestClient<ChatClient>(TestScenario.Chat);
+
+        ChatCompletionOptions options = new()
+        {
+            PredictedContent =
+            [
+                ChatMessageContentPart.CreateTextPart("""
+                {
+                  "feature_name": "test_feature",
+                  "enabled": true
+                }
+                """.ReplaceLineEndings("\n")),
+            ],
+        };
+
+        ChatMessage message = ChatMessage.CreateUserMessage("""
+            Modify the following input to enable the feature. Only respond with the JSON and include no other text.
+
+            {
+              "feature_name": "test_feature",
+              "enabled": false
+            }
+            """.ReplaceLineEndings("\n"));
+
+        ChatCompletion completion = await client.CompleteChatAsync([message], options);
+
+        Assert.That(completion.Usage.OutputTokenDetails.AcceptedPredictionTokenCount, Is.GreaterThan(0));
+    }
 }