Provide method to create TestRestTemplate with basic auth from existing

Closes gh-6732

spring-boot-test/src/main/java/org/springframework/boot/test/web/client/TestRestTemplate.java

@@ -18,9 +18,11 @@ package org.springframework.boot.test.web.client;
 
 import java.io.IOException;
 import java.net.URI;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashSet;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -82,6 +84,8 @@ public class TestRestTemplate {
 
 	private final RestTemplate restTemplate;
 
+	private final HttpClientOption[] httpClientOptions;
+
 	/**
 	 * Create a new {@link TestRestTemplate} instance.
 	 * @param restTemplateBuilder builder used to configure underlying
@@ -118,6 +122,7 @@ public class TestRestTemplate {
 	public TestRestTemplate(RestTemplate restTemplate, String username, String password,
 			HttpClientOption... httpClientOptions) {
 		Assert.notNull(restTemplate, "RestTemplate must not be null");
+		this.httpClientOptions = httpClientOptions;
 		if (ClassUtils.isPresent("org.apache.http.client.config.RequestConfig", null)) {
 			restTemplate.setRequestFactory(
 					new CustomHttpComponentsClientHttpRequestFactory(httpClientOptions));
@@ -900,6 +905,40 @@ public class TestRestTemplate {
 		return this.restTemplate;
 	}
 
+	/**
+	 * Creates a new {@code TestRestTemplate} with the same configuration as this one,
+	 * except that it will send basic authorization headers using the given
+	 * {@code username} and {@code password}.
+	 * @param username the username
+	 * @param password the password
+	 * @return the new template
+	 * @since 1.4.1
+	 */
+	public TestRestTemplate withBasicAuth(String username, String password) {
+		RestTemplate restTemplate = new RestTemplate();
+		restTemplate.setErrorHandler(getRestTemplate().getErrorHandler());
+		restTemplate.setMessageConverters(getRestTemplate().getMessageConverters());
+		restTemplate.setInterceptors(
+				removeBasicAuthInterceptorIfPresent(getRestTemplate().getInterceptors()));
+		restTemplate.setRequestFactory(getRestTemplate().getRequestFactory());
+		restTemplate.setUriTemplateHandler(getRestTemplate().getUriTemplateHandler());
+		return new TestRestTemplate(restTemplate, username, password,
+				this.httpClientOptions);
+	}
+
+	private List<ClientHttpRequestInterceptor> removeBasicAuthInterceptorIfPresent(
+			List<ClientHttpRequestInterceptor> interceptors) {
+		List<ClientHttpRequestInterceptor> updatedInterceptors = new ArrayList<ClientHttpRequestInterceptor>(
+				interceptors);
+		Iterator<ClientHttpRequestInterceptor> iterator = updatedInterceptors.iterator();
+		while (iterator.hasNext()) {
+			if (iterator.next() instanceof BasicAuthorizationInterceptor) {
+				iterator.remove();
+			}
+		}
+		return interceptors;
+	}
+
 	/**
 	 * Options used to customize the Apache Http Client if it is used.
 	 */