Polish "Validate node configuration with static master replica"

See gh-47401

Author: snicoll

module/spring-boot-data-redis/src/test/java/org/springframework/boot/data/redis/autoconfigure/DataRedisAutoConfigurationTests.java

@@ -500,6 +500,15 @@ void testRedisConfigurationWithClusterAndAuthentication() {
 			});
 	}
 
+	@Test
+	void testRedisConfigurationWithMasterReplicaAndNoNode() {
+		this.contextRunner.withPropertyValues("spring.data.redis.masterreplica.nodes=")
+			.run((context) -> assertThat(context).hasFailed()
+				.getFailure()
+				.rootCause()
+				.hasMessage("At least one node is required for master-replica configuration"));
+	}
+
 	@Test
 	void testRedisConfigurationWithMasterReplica() {
 		this.contextRunner