Updated the docs to use tests; fixes gh-2187

docs/src/main/asciidoc/project-features.adoc

@@ -288,21 +288,12 @@ spring.zipkin.sender.type: web
 
 If you're running a non-reactive application we will use a `RestTemplate` based span sender. Otherwise a `WebClient` based span sender will be chosen.
 
-To customize the `RestTemplate` that sends spans to Zipkin via HTTP, you can register the `ZipkinRestTemplateCustomizer` bean.
+To customize the `RestTemplate` that sends spans to Zipkin via HTTP, you can register the `ZipkinRestTemplateCustomizer` bean in your `@Configuration` annotated Spring configuration class.
 
 [source,java,indent=0]
 ----
-@Configuration(proxyBeanMethods = false)
-	class MyConfig {
-	@Bean ZipkinRestTemplateCustomizer myCustomizer() {
-		return new ZipkinRestTemplateCustomizer() {
-			@Override
-			void customize(RestTemplate restTemplate) {
-				// customize the RestTemplate
-			}
-		};
-	}
-}
+include::{autoconfig_path}/src/test/java/org/springframework/cloud/sleuth/autoconfig/zipkin2/ZipkinHttpSenderConfigurationTests.java[tags=customizer_1,indent=0]
+include::{autoconfig_path}/src/test/java/org/springframework/cloud/sleuth/autoconfig/zipkin2/ZipkinHttpSenderConfigurationTests.java[tags=customizer_2,indent=0]
 ----
 
 If, however, you would like to control the full process of creating the `RestTemplate`
@@ -310,10 +301,7 @@ object, you will have to create a bean of `ZipkinRestTemplateProvider` type.
 
 [source,java,indent=0]
 ----
-	@Bean
-	ZipkinRestTemplateProvider myZipkinRestTemplateProvider() {
-		return MyRestTemplate::new;
-	}
+include::{autoconfig_path}/src/test/java/org/springframework/cloud/sleuth/autoconfig/zipkin2/ZipkinHttpSenderConfigurationTests.java[tags=provider,indent=0]
 ----
 
 By default, api path will be set to `api/v2/spans` or `api/v1/spans` depending on the encoder version. If you want to use a custom api path, you can configure it using the following property (empty case, set ""):

spring-cloud-sleuth-autoconfigure/src/test/java/org/springframework/cloud/sleuth/autoconfig/zipkin2/ZipkinHttpSenderConfigurationTests.java

@@ -47,22 +47,30 @@ class ZipkinHttpSenderConfigurationTests {
 
 		boolean customizerCalled;
 
+
+		// tag::provider[]
 		@Bean
 		ZipkinRestTemplateProvider myZipkinRestTemplateProvider() {
 			return MyRestTemplate::new;
 		}
+		// end::provider[]
 
+		// tag::customizer_1[]
 		@Bean
 		ZipkinRestTemplateCustomizer myZipkinRestTemplateCustomizer() {
 			return new ZipkinRestTemplateCustomizer() {
 				@Override
 				public RestTemplate customizeTemplate(RestTemplate restTemplate) {
+					// end::customizer_1[]
 					customizerCalled = true;
 					BDDAssertions.then(restTemplate).isInstanceOf(MyRestTemplate.class);
+					// tag::customizer_2[]
+					// customize the RestTemplate
 					return restTemplate;
 				}
 			};
 		}
+		// end::customizer_2[]
 
 	}