test: Add improving test coverage for MultiQueryExpander, StreamHelper, and Query classes (#4473)

* test: Add missing test coverage for MultiQueryExpander, StreamHelper, and Query classes

Co-authored-by: Oleksandr Klymenko <alexanderklmn@gmail.com>
Signed-off-by: Oleksandr Klymenko <alexanderklmn@gmail.com>

Author: alxkm

models/spring-ai-anthropic/src/test/java/org/springframework/ai/anthropic/api/StreamHelperTests.java

@@ -59,4 +59,17 @@ void testMultipleErrorEventsHandling() {
 		assertThat(response2).isNotNull();
 	}
 
+	@Test
+	void testPingEventHandling() {
+		StreamHelper streamHelper = new StreamHelper();
+		AtomicReference<ChatCompletionResponseBuilder> contentBlockReference = new AtomicReference<>();
+
+		AnthropicApi.PingEvent pingEvent = new AnthropicApi.PingEvent(AnthropicApi.EventType.PING);
+
+		AnthropicApi.ChatCompletionResponse response = streamHelper.eventToChatCompletionResponse(pingEvent,
+				contentBlockReference);
+
+		assertThat(response).isNotNull();
+	}
+
 }

spring-ai-rag/src/test/java/org/springframework/ai/rag/QueryTests.java

@@ -78,4 +78,22 @@ void whenCompareQueryToNullThenNotEqual() {
 		assertThat(query).isNotEqualTo(null);
 	}
 
+	@Test
+	void whenCompareQueryToDifferentTypeThenNotEqual() {
+		Query query = new Query("Test query");
+		String notAQuery = "Test query";
+
+		assertThat(query).isNotEqualTo(notAQuery);
+	}
+
+	@Test
+	void toStringReturnsExpectedFormat() {
+		Query query = new Query("Test query text");
+		String toString = query.toString();
+
+		assertThat(toString).contains("Query");
+		assertThat(toString).contains("text");
+		assertThat(toString).contains("Test query text");
+	}
+
 }

spring-ai-rag/src/test/java/org/springframework/ai/rag/preretrieval/query/expansion/MultiQueryExpanderTests.java

@@ -22,6 +22,7 @@
 import org.springframework.ai.chat.prompt.PromptTemplate;
 
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
 import static org.mockito.Mockito.mock;
 
 /**
@@ -69,4 +70,19 @@ void whenPromptHasMissingQueryPlaceholderThenThrow() {
 			.hasMessageContaining("query");
 	}
 
+	@Test
+	void whenBuilderIsNullThenThrow() {
+		assertThatThrownBy(() -> MultiQueryExpander.builder().build()).isInstanceOf(IllegalArgumentException.class)
+			.hasMessageContaining("chatClientBuilder cannot be null");
+	}
+
+	@Test
+	void whenPromptTemplateIsNullThenUseDefault() {
+		MultiQueryExpander queryExpander = MultiQueryExpander.builder()
+			.chatClientBuilder(mock(ChatClient.Builder.class))
+			.promptTemplate(null)
+			.build();
+		assertThat(queryExpander).isNotNull();
+	}
+
 }