Provide access to root URI from TestRestTemplate

Closes gh-10641

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/web/client/TestRestTemplateTests.java

@@ -63,6 +63,7 @@ import static org.mockito.Mockito.verify;
  * @author Phillip Webb
  * @author Stephane Nicoll
  * @author Andy Wilkinson
+ * @author Kristine Jetzke
  */
 public class TestRestTemplateTests {
 
@@ -81,6 +82,31 @@ public class TestRestTemplateTests {
 				.isInstanceOf(HttpComponentsClientHttpRequestFactory.class);
 	}
 
+	@Test
+	public void getRootUriRootUriSetViaRestTemplateBuilder() {
+		String rootUri = "http://example.com";
+		RestTemplate delegate = new RestTemplateBuilder().rootUri(rootUri).build();
+
+		assertThat(new TestRestTemplate(delegate).getRootUri()).isEqualTo(rootUri);
+	}
+
+	@Test
+	public void getRootUriRootUriSetViaLocalHostUriTemplateHandler() {
+		String rootUri = "http://example.com";
+		TestRestTemplate template = new TestRestTemplate();
+		LocalHostUriTemplateHandler templateHandler = mock(
+				LocalHostUriTemplateHandler.class);
+		given(templateHandler.getRootUri()).willReturn(rootUri);
+		template.setUriTemplateHandler(templateHandler);
+
+		assertThat(template.getRootUri()).isEqualTo(rootUri);
+	}
+
+	@Test
+	public void getRootUriRootUriNotSet() {
+		assertThat(new TestRestTemplate().getRootUri()).isEqualTo("");
+	}
+
 	@Test
 	public void authenticated() {
 		assertThat(new TestRestTemplate("user", "password").getRestTemplate()