refactor: reuse Vaadin environment for PER_CLASS Spring tests

spring/src/main/java/com/vaadin/browserless/SpringBrowserlessTest.java

@@ -17,8 +17,6 @@
 
 import java.util.Set;
 
-import org.junit.jupiter.api.AfterEach;
-import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.ApplicationContext;
@@ -62,7 +60,7 @@
  * }
  * </pre>
  */
-@ExtendWith({ SpringExtension.class })
+@ExtendWith({ SpringExtension.class, BrowserlessTestExtension.class })
 @TestExecutionListeners(listeners = BrowserlessTestSpringLookupInitializer.class, mergeMode = TestExecutionListeners.MergeMode.MERGE_WITH_DEFAULTS)
 public abstract class SpringBrowserlessTest extends BaseBrowserlessTest
         implements TesterWrappers {
@@ -82,13 +80,19 @@ protected Set<Class<?>> lookupServices() {
     }
 
     /**
-     * Sets up the mock Vaadin Spring environment before each test. Runs as a
-     * {@code @BeforeEach} method so that it fires <em>after</em> all JUnit 5
-     * extension {@code beforeEach} callbacks — in particular after
-     * {@code SpringExtension.beforeEach()}, which populates the Spring Security
-     * context for annotations such as {@code @WithMockUser}.
+     * Sets up the mock Vaadin Spring environment.
+     * <p>
+     * The lifecycle is driven by {@link BrowserlessTestExtension}: for the
+     * default per-method lifecycle it is invoked from the extension's
+     * {@code beforeEach} callback, and for {@code @TestInstance(PER_CLASS)}
+     * from {@code beforeAll}, so the environment is created once and reused
+     * across the test methods.
+     * <p>
+     * {@link BrowserlessTestExtension} is declared <em>after</em>
+     * {@link SpringExtension} in {@code @ExtendWith} so that this init fires
+     * after {@code SpringExtension.beforeEach()}, which populates the Spring
+     * Security context for annotations such as {@code @WithMockUser}.
      */
-    @BeforeEach
     @Override
     protected void initVaadinEnvironment() {
         scanTesters();
@@ -98,7 +102,16 @@ protected void initVaadinEnvironment() {
         initSignalsSupport();
     }
 
-    @AfterEach
+    /**
+     * Tears down the mock Vaadin Spring environment.
+     * <p>
+     * The lifecycle is driven by {@link BrowserlessTestExtension}: for the
+     * default per-method lifecycle it is invoked from the extension's
+     * {@code afterEach} callback, and for {@code @TestInstance(PER_CLASS)} from
+     * {@code afterAll}, so the environment created in
+     * {@link #initVaadinEnvironment()} is torn down once after all test
+     * methods.
+     */
     @Override
     protected void cleanVaadinEnvironment() {
         super.cleanVaadinEnvironment();

spring/src/test/java/com/vaadin/browserless/SpringBrowserlessPerClassLifecycleTest.java

@@ -16,32 +16,60 @@
 package com.vaadin.browserless;
 
 import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestInstance;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.test.context.ContextConfiguration;
 
+import com.vaadin.flow.component.UI;
 import com.vaadin.flow.server.VaadinService;
 import com.vaadin.flow.server.VaadinSession;
 
+/**
+ * Verifies that {@link SpringBrowserlessTest} combined with
+ * {@code @TestInstance(PER_CLASS)} creates the Vaadin environment once and
+ * reuses the same {@link VaadinService}, {@link VaadinSession} and {@link UI}
+ * across all test methods in the class.
+ */
 @TestInstance(TestInstance.Lifecycle.PER_CLASS)
 @ContextConfiguration(classes = SpringBrowserlessPerClassLifecycleTest.TestConfig.class)
 class SpringBrowserlessPerClassLifecycleTest extends SpringBrowserlessTest {
 
+    private VaadinService sharedService;
+    private VaadinSession sharedSession;
+    private UI sharedUI;
+
+    @BeforeAll
+    void captureVaadinEnvironment() {
+        sharedService = VaadinService.getCurrent();
+        sharedSession = VaadinSession.getCurrent();
+        sharedUI = UI.getCurrent();
+        Assertions.assertNotNull(sharedService,
+                "VaadinService should be available after PER_CLASS init");
+        Assertions.assertNotNull(sharedSession,
+                "VaadinSession should be available after PER_CLASS init");
+        Assertions.assertNotNull(sharedUI,
+                "UI should be available after PER_CLASS init");
+    }
+
     @Test
-    void perClassLifecycle_firstTest_vaadinEnvironmentIsSetup() {
-        Assertions.assertNotNull(VaadinService.getCurrent(),
-                "VaadinService should be available with PER_CLASS lifecycle");
-        Assertions.assertNotNull(VaadinSession.getCurrent(),
-                "VaadinSession should be available with PER_CLASS lifecycle");
+    void firstTest_sameVaadinEnvironment() {
+        assertSameEnvironment();
     }
 
     @Test
-    void perClassLifecycle_secondTest_vaadinEnvironmentIsSetup() {
-        Assertions.assertNotNull(VaadinService.getCurrent(),
-                "VaadinService should be available with PER_CLASS lifecycle");
-        Assertions.assertNotNull(VaadinSession.getCurrent(),
-                "VaadinSession should be available with PER_CLASS lifecycle");
+    void secondTest_sameVaadinEnvironment() {
+        assertSameEnvironment();
+    }
+
+    private void assertSameEnvironment() {
+        Assertions.assertSame(sharedService, VaadinService.getCurrent(),
+                "PER_CLASS lifecycle must reuse the same VaadinService across tests");
+        Assertions.assertSame(sharedSession, VaadinSession.getCurrent(),
+                "PER_CLASS lifecycle must reuse the same VaadinSession across tests");
+        Assertions.assertSame(sharedUI, UI.getCurrent(),
+                "PER_CLASS lifecycle must reuse the same UI across tests");
     }
 
     @Configuration