Use Gradle test fixture support for spring-core

See gh-23550

spring-test/src/test/java/org/springframework/test/context/junit4/concurrency/SpringJUnit4ConcurrencyTests.java

@@ -24,6 +24,7 @@ import org.junit.Ignore;
 import org.junit.Test;
 import org.junit.experimental.ParallelComputer;
 
+import org.springframework.core.test.fixtures.TestGroup;
 import org.springframework.test.context.junit4.InheritedConfigSpringJUnit4ClassRunnerAppCtxTests;
 import org.springframework.test.context.junit4.MethodLevelTransactionalSpringRunnerTests;
 import org.springframework.test.context.junit4.SpringJUnit47ClassRunnerRuleTests;
@@ -34,7 +35,6 @@ import org.springframework.test.context.junit4.rules.BaseAppCtxRuleTests;
 import org.springframework.test.context.junit4.rules.BasicAnnotationConfigWacSpringRuleTests;
 import org.springframework.test.context.junit4.rules.SpringClassRule;
 import org.springframework.test.context.junit4.rules.SpringMethodRule;
-import org.springframework.tests.TestGroup;
 import org.springframework.util.ReflectionUtils;
 
 import static org.junit.Assume.assumeTrue;

spring-test/src/test/java/org/springframework/test/web/reactive/server/HttpHandlerConnectorTests.java

@@ -28,7 +28,7 @@ import reactor.core.scheduler.Schedulers;
 
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DefaultDataBufferFactory;
-import org.springframework.core.io.buffer.support.DataBufferTestUtils;
+import org.springframework.core.test.fixtures.io.buffer.DataBufferTestUtils;
 import org.springframework.http.HttpCookie;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;

spring-test/src/test/java/org/springframework/test/web/servlet/htmlunit/DelegatingWebConnectionTests.java

@@ -32,17 +32,17 @@ import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.Mock;
 import org.mockito.junit.jupiter.MockitoExtension;
 
+import org.springframework.core.test.fixtures.EnabledForTestGroups;
 import org.springframework.stereotype.Controller;
 import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.test.web.servlet.htmlunit.DelegatingWebConnection.DelegateWebConnection;
 import org.springframework.test.web.servlet.setup.MockMvcBuilders;
-import org.springframework.tests.EnabledForTestGroups;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.BDDMockito.given;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
-import static org.springframework.tests.TestGroup.PERFORMANCE;
+import static org.springframework.core.test.fixtures.TestGroup.PERFORMANCE;
 
 /**
  * Unit and integration tests for {@link DelegatingWebConnection}.

spring-test/src/test/java/org/springframework/test/web/servlet/htmlunit/MockMvcWebClientBuilderTests.java

@@ -30,10 +30,10 @@ import com.gargoylesoftware.htmlunit.util.Cookie;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.test.fixtures.TestGroup;
 import org.springframework.test.context.junit.jupiter.web.SpringJUnitWebConfig;
 import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.test.web.servlet.setup.MockMvcBuilders;
-import org.springframework.tests.TestGroup;
 import org.springframework.web.bind.annotation.CookieValue;
 import org.springframework.web.bind.annotation.DeleteMapping;
 import org.springframework.web.bind.annotation.PostMapping;

spring-test/src/test/java/org/springframework/test/web/servlet/htmlunit/webdriver/MockMvcHtmlUnitDriverBuilderTests.java

@@ -25,10 +25,10 @@ import org.junit.jupiter.api.Test;
 import org.openqa.selenium.htmlunit.HtmlUnitDriver;
 
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.test.fixtures.TestGroup;
 import org.springframework.test.context.junit.jupiter.web.SpringJUnitWebConfig;
 import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.test.web.servlet.setup.MockMvcBuilders;
-import org.springframework.tests.TestGroup;
 import org.springframework.web.bind.annotation.CookieValue;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;