Polish "Fix request factory used with withBasicAuth"

Fixes gh-15982

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

@@ -1027,10 +1027,8 @@ public class TestRestTemplate {
 	/**
 	 * 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}. Note, that a new instance of
-	 * {@link ClientHttpRequestFactory} will be created (if possible) based on the current
-	 * factory class, otherwise {@link ClientHttpRequestFactorySupplier} will be used to
-	 * instantiate a {@link ClientHttpRequestFactory}.
+	 * {@code username} and {@code password}. The request factory used is a new instance
+	 * of the underlying {@link RestTemplate}'s request factory type (when possible).
 	 * @param username the username
 	 * @param password the password
 	 * @return the new template

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

@@ -33,6 +33,7 @@ import org.springframework.http.HttpEntity;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.RequestEntity;
+import org.springframework.http.client.ClientHttpRequest;
 import org.springframework.http.client.ClientHttpRequestFactory;
 import org.springframework.http.client.ClientHttpRequestInterceptor;
 import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
@@ -97,7 +98,7 @@ public class TestRestTemplateTests {
 	public void useTheSameRequestFactoryClassWithBasicAuth() {
 		OkHttp3ClientHttpRequestFactory customFactory = new OkHttp3ClientHttpRequestFactory();
 		RestTemplateBuilder builder = new RestTemplateBuilder()
-				.requestFactory(OkHttp3ClientHttpRequestFactory::new);
+				.requestFactory(() -> customFactory);
 		TestRestTemplate testRestTemplate = new TestRestTemplate(builder)
 				.withBasicAuth("test", "test");
 		RestTemplate restTemplate = testRestTemplate.getRestTemplate();
@@ -107,6 +108,21 @@ public class TestRestTemplateTests {
 				.hasSameClassAs(customFactory);
 	}
 
+	@Test
+	public void withBasicAuthWhenRequestFactoryTypeCannotBeInstantiatedShouldFallback() {
+		TestClientHttpRequestFactory customFactory = new TestClientHttpRequestFactory(
+				"my-request-factory");
+		RestTemplateBuilder builder = new RestTemplateBuilder()
+				.requestFactory(() -> customFactory);
+		TestRestTemplate testRestTemplate = new TestRestTemplate(builder)
+				.withBasicAuth("test", "test");
+		RestTemplate restTemplate = testRestTemplate.getRestTemplate();
+		Object requestFactory = ReflectionTestUtils
+				.getField(restTemplate.getRequestFactory(), "requestFactory");
+		assertThat(requestFactory).isNotEqualTo(customFactory)
+				.isInstanceOf(CustomHttpComponentsClientHttpRequestFactory.class);
+	}
+
 	@Test
 	public void getRootUriRootUriSetViaRestTemplateBuilder() {
 		String rootUri = "http://example.com";
@@ -397,4 +413,17 @@ public class TestRestTemplateTests {
 
 	}
 
+	static class TestClientHttpRequestFactory implements ClientHttpRequestFactory {
+
+		TestClientHttpRequestFactory(String value) {
+		}
+
+		@Override
+		public ClientHttpRequest createRequest(URI uri, HttpMethod httpMethod)
+				throws IOException {
+			return null;
+		}
+
+	}
+
 }