Adds test case.

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/redis/TraceRedisAutoConfiguration.java

@@ -75,7 +75,9 @@ class TraceLettuceClientResourcesBeanPostProcessor implements BeanPostProcessor
 			throws BeansException {
 		if (bean instanceof ClientResources) {
 			ClientResources cr = (ClientResources) bean;
-			if (cr.tracing() == null) {
+			// tracing of ClientResources instance created by default is `disabled()`
+			if (cr.tracing() == null
+					|| cr.tracing() == io.lettuce.core.tracing.Tracing.disabled()) {
 				return cr.mutate().tracing(BraveTracing.create(this.tracing)).build();
 			}
 		}

spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/instrument/redis/TraceRedisAutoConfigurationTests.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2013-2019 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
+ *
+ *      http://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.cloud.sleuth.instrument.redis;
+
+import brave.Tracing;
+import io.lettuce.core.resource.ClientResources;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.assertj.core.api.BDDAssertions.then;
+
+/**
+ * @author Chao Chang
+ */
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = TraceRedisAutoConfigurationTests.Config.class, webEnvironment = SpringBootTest.WebEnvironment.NONE)
+public class TraceRedisAutoConfigurationTests {
+
+	@Autowired
+	ClientResources clientResources;
+
+	@Autowired
+	TestTraceLettuceClientResourcesBeanPostProcessor traceLettuceClientResourcesBeanPostProcessor;
+
+	@Test
+	public void tracing_should_be_set() {
+		then(this.traceLettuceClientResourcesBeanPostProcessor.tracingCalled).isTrue();
+		then(this.clientResources.tracing()).isNotNull();
+		then(this.clientResources.tracing())
+				.isNotSameAs(io.lettuce.core.tracing.Tracing.disabled());
+	}
+
+	@Configuration
+	@EnableAutoConfiguration
+	protected static class Config {
+
+		@Bean
+		ClientResources clientResources() {
+			ClientResources clientResources = ClientResources.create();
+			then(clientResources.tracing())
+					.isSameAs(io.lettuce.core.tracing.Tracing.disabled());
+			return clientResources;
+		}
+
+		@Bean
+		TestTraceLettuceClientResourcesBeanPostProcessor testTraceLettuceClientResourcesBeanPostProcessor(
+				Tracing tracing) {
+			return new TestTraceLettuceClientResourcesBeanPostProcessor(tracing);
+		}
+
+	}
+
+}
+
+class TestTraceLettuceClientResourcesBeanPostProcessor
+		extends TraceLettuceClientResourcesBeanPostProcessor {
+
+	boolean tracingCalled = false;
+
+	TestTraceLettuceClientResourcesBeanPostProcessor(Tracing tracing) {
+		super(tracing);
+	}
+
+	@Override
+	public Object postProcessAfterInitialization(Object bean, String beanName)
+			throws BeansException {
+		this.tracingCalled = true;
+		return super.postProcessAfterInitialization(bean, beanName);
+	}
+
+}