diff --git a/models/spring-ai-openai/src/test/java/org/springframework/ai/openai/api/OpenAiStreamFunctionCallingHelperTest.java b/models/spring-ai-openai/src/test/java/org/springframework/ai/openai/api/OpenAiStreamFunctionCallingHelperTest.java
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+++ b/models/spring-ai-openai/src/test/java/org/springframework/ai/openai/api/OpenAiStreamFunctionCallingHelperTest.java
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+/*
+ * Copyright 2023-2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.ai.openai.api;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.function.Consumer;
+import static org.assertj.core.api.Assertions.assertThat;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+
+/**
+ * Unit tests for {@link OpenAiStreamFunctionCallingHelper}
+ *
+ * @author Emmanuel Essien-nta
+ */
+public class OpenAiStreamFunctionCallingHelperTest {
+
+	private final OpenAiStreamFunctionCallingHelper helper = new OpenAiStreamFunctionCallingHelper();
+
+	@Test
+	public void merge_whenInputIsValid() {
+		var expectedResult = new OpenAiApi.ChatCompletionChunk("id", Collections.emptyList(),
+				System.currentTimeMillis(), "model", "serviceTier", "fingerPrint", "object", null);
+		var previous = new OpenAiApi.ChatCompletionChunk(null, null, expectedResult.created(), expectedResult.model(),
+				expectedResult.serviceTier(), null, null, null);
+		var current = new OpenAiApi.ChatCompletionChunk(expectedResult.id(), null, null, null, null,
+				expectedResult.systemFingerprint(), expectedResult.object(), expectedResult.usage());
+
+		var result = helper.merge(previous, current);
+		assertThat(result).isEqualTo(expectedResult);
+	}
+
+	@Test
+	public void isStreamingToolFunctionCall_whenChatCompletionChunkIsNull() {
+		assertThat(helper.isStreamingToolFunctionCall(null)).isFalse();
+	}
+
+	@Test
+	public void isStreamingToolFunctionCall_whenChatCompletionChunkChoicesIsEmpty() {
+		var chunk = new OpenAiApi.ChatCompletionChunk(null, Collections.emptyList(), null, null, null, null, null,
+				null);
+		assertThat(helper.isStreamingToolFunctionCall(chunk)).isFalse();
+	}
+
+	@Test
+	public void isStreamingToolFunctionCall_whenChatCompletionChunkFirstChoiceIsNull() {
+		var choice = (org.springframework.ai.openai.api.OpenAiApi.ChatCompletionChunk.ChunkChoice) null;
+		var chunk = new OpenAiApi.ChatCompletionChunk(null, Arrays.asList(choice), null, null, null, null, null, null);
+		assertThat(helper.isStreamingToolFunctionCall(chunk)).isFalse();
+	}
+
+	@Test
+	public void isStreamingToolFunctionCall_whenChatCompletionChunkFirstChoiceDeltaIsNull() {
+		var choice = new org.springframework.ai.openai.api.OpenAiApi.ChatCompletionChunk.ChunkChoice(null, null, null,
+				null);
+		var chunk = new OpenAiApi.ChatCompletionChunk(null, Arrays.asList(choice, null), null, null, null, null, null,
+				null);
+		assertThat(helper.isStreamingToolFunctionCall(chunk)).isFalse();
+	}
+
+	@Test
+	public void isStreamingToolFunctionCall_whenChatCompletionChunkFirstChoiceDeltaToolCallsIsNullOrEmpty() {
+		var assertion = (Consumer<OpenAiApi.ChatCompletionMessage>) (OpenAiApi.ChatCompletionMessage delta) -> {
+			var choice = new org.springframework.ai.openai.api.OpenAiApi.ChatCompletionChunk.ChunkChoice(null, null,
+					delta, null);
+			var chunk = new OpenAiApi.ChatCompletionChunk(null, List.of(choice), null, null, null, null, null, null);
+			assertThat(helper.isStreamingToolFunctionCall(chunk)).isFalse();
+		};
+		// Test for null.
+		assertion.accept(new OpenAiApi.ChatCompletionMessage(null, null));
+		// Test for empty.
+		assertion.accept(
+				new OpenAiApi.ChatCompletionMessage(null, null, null, null, Collections.emptyList(), null, null, null));
+	}
+
+	@Test
+	public void isStreamingToolFunctionCall_whenChatCompletionChunkFirstChoiceDeltaToolCallsIsNonEmpty() {
+		var assertion = (Consumer<OpenAiApi.ChatCompletionMessage>) (OpenAiApi.ChatCompletionMessage delta) -> {
+			var choice = new org.springframework.ai.openai.api.OpenAiApi.ChatCompletionChunk.ChunkChoice(null, null,
+					delta, null);
+			var chunk = new OpenAiApi.ChatCompletionChunk(null, List.of(choice), null, null, null, null, null, null);
+			assertThat(helper.isStreamingToolFunctionCall(chunk)).isTrue();
+		};
+		assertion.accept(new OpenAiApi.ChatCompletionMessage(null, null, null, null,
+				List.of(Mockito.mock(org.springframework.ai.openai.api.OpenAiApi.ChatCompletionMessage.ToolCall.class)),
+				null, null, null));
+	}
+
+	@Test
+	public void isStreamingToolFunctionCallFinish_whenChatCompletionChunkIsNull() {
+		assertThat(helper.isStreamingToolFunctionCallFinish(null)).isFalse();
+	}
+
+	@Test
+	public void isStreamingToolFunctionCallFinish_whenChatCompletionChunkChoicesIsEmpty() {
+		var chunk = new OpenAiApi.ChatCompletionChunk(null, Collections.emptyList(), null, null, null, null, null,
+				null);
+		assertThat(helper.isStreamingToolFunctionCallFinish(chunk)).isFalse();
+	}
+
+	@Test
+	public void isStreamingToolFunctionCallFinish_whenChatCompletionChunkFirstChoiceIsNull() {
+		var choice = (org.springframework.ai.openai.api.OpenAiApi.ChatCompletionChunk.ChunkChoice) null;
+		var chunk = new OpenAiApi.ChatCompletionChunk(null, Arrays.asList(choice), null, null, null, null, null, null);
+		assertThat(helper.isStreamingToolFunctionCallFinish(chunk)).isFalse();
+	}
+
+	@Test
+	public void isStreamingToolFunctionCallFinish_whenChatCompletionChunkFirstChoiceDeltaIsNull() {
+		var choice = new org.springframework.ai.openai.api.OpenAiApi.ChatCompletionChunk.ChunkChoice(null, null, null,
+				null);
+		var chunk = new OpenAiApi.ChatCompletionChunk(null, Arrays.asList(choice, null), null, null, null, null, null,
+				null);
+		assertThat(helper.isStreamingToolFunctionCallFinish(chunk)).isFalse();
+	}
+
+	@Test
+	public void isStreamingToolFunctionCallFinish_whenChatCompletionChunkFirstChoiceIsNotToolCalls() {
+		var choice = new org.springframework.ai.openai.api.OpenAiApi.ChatCompletionChunk.ChunkChoice(null, null,
+				new OpenAiApi.ChatCompletionMessage(null, null), null);
+		var chunk = new OpenAiApi.ChatCompletionChunk(null, List.of(choice), null, null, null, null, null, null);
+		assertThat(helper.isStreamingToolFunctionCallFinish(chunk)).isFalse();
+	}
+
+	@Test
+	public void isStreamingToolFunctionCallFinish_whenChatCompletionChunkFirstChoiceIsToolCalls() {
+		var choice = new org.springframework.ai.openai.api.OpenAiApi.ChatCompletionChunk.ChunkChoice(
+				OpenAiApi.ChatCompletionFinishReason.TOOL_CALLS, null, new OpenAiApi.ChatCompletionMessage(null, null),
+				null);
+		var chunk = new OpenAiApi.ChatCompletionChunk(null, List.of(choice), null, null, null, null, null, null);
+		assertThat(helper.isStreamingToolFunctionCallFinish(chunk)).isTrue();
+	}
+
+	@Test
+	public void chunkToChatCompletion_whenInputIsValid() {
+		var choice1 = new org.springframework.ai.openai.api.OpenAiApi.ChatCompletionChunk.ChunkChoice(
+				OpenAiApi.ChatCompletionFinishReason.TOOL_CALLS, 1, new OpenAiApi.ChatCompletionMessage(null, null),
+				null);
+		var choice2 = new org.springframework.ai.openai.api.OpenAiApi.ChatCompletionChunk.ChunkChoice(
+				OpenAiApi.ChatCompletionFinishReason.TOOL_CALLS, 2, new OpenAiApi.ChatCompletionMessage(null, null),
+				null);
+		var chunk = new OpenAiApi.ChatCompletionChunk(null, List.of(choice1, choice2), null, null, null, null, null,
+				null);
+		OpenAiApi.ChatCompletion result = helper.chunkToChatCompletion(chunk);
+		assertThat(result.object()).isEqualTo("chat.completion");
+		assertThat(result.choices()).hasSize(2);
+	}
+
+}
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