Minor improvements in spring-test

- Remove final modifier from private method
- Use StandardCharsets
- Remove unnecessary toString calls
- Remove unnecessary static modifiers
- Refactor to use enhanced switch
- Replace concatenated strings with text blocks
- Rely on auto-boxing where appropriate
- Remove unnecessary code
- Fix imports in Kotlin test classes

Closes gh-29413

Author: imkulwant

spring-test/src/main/java/org/springframework/test/context/junit/jupiter/AbstractExpressionEvaluatingCondition.java

@@ -93,7 +93,7 @@ protected <A extends Annotation> ConditionEvaluationResult evaluateAnnotation(Cl
 		AnnotatedElement element = context.getElement().get();
 		Optional<A> annotation = findMergedAnnotation(element, annotationType);
 
-		if (!annotation.isPresent()) {
+		if (annotation.isEmpty()) {
 			String reason = String.format("%s is enabled since @%s is not present", element,
 					annotationType.getSimpleName());
 			if (logger.isDebugEnabled()) {

spring-test/src/main/java/org/springframework/test/context/support/AbstractGenericContextLoader.java

@@ -188,7 +188,7 @@ else if (logger.isDebugEnabled()) {
 	 * register a JVM shutdown hook for it
 	 * @return a new application context
 	 */
-	private final GenericApplicationContext loadContext(
+	private GenericApplicationContext loadContext(
 			MergedContextConfiguration mergedConfig, boolean forAotProcessing) throws Exception {
 
 		if (logger.isTraceEnabled()) {

spring-test/src/main/java/org/springframework/test/context/testng/AbstractTestNGSpringContextTests.java

@@ -201,7 +201,7 @@ protected void springTestContextAfterTestClass() throws Exception {
 	private Throwable getTestResultException(ITestResult testResult) {
 		Throwable testResultException = testResult.getThrowable();
 		if (testResultException instanceof InvocationTargetException) {
-			testResultException = ((InvocationTargetException) testResultException).getCause();
+			testResultException = testResultException.getCause();
 		}
 		return testResultException;
 	}

spring-test/src/main/java/org/springframework/test/util/XmlExpectationsHelper.java

@@ -82,7 +82,7 @@ public void assertSource(String content, Matcher<? super Source> matcher) throws
 	public void assertXmlEqual(String expected, String actual) throws Exception {
 		XmlUnitDiff diff = new XmlUnitDiff(expected, actual);
 		if (diff.hasDifferences()) {
-			AssertionErrors.fail("Body content " + diff.toString());
+			AssertionErrors.fail("Body content " + diff);
 		}
 	}
 

spring-test/src/test/java/org/springframework/test/context/configuration/interfaces/BootstrapWithTestInterface.java

@@ -34,7 +34,7 @@
 @BootstrapWith(CustomTestContextBootstrapper.class)
 interface BootstrapWithTestInterface {
 
-	static class CustomTestContextBootstrapper extends DefaultTestContextBootstrapper {
+	class CustomTestContextBootstrapper extends DefaultTestContextBootstrapper {
 
 		@Override
 		protected List<ContextCustomizerFactory> getContextCustomizerFactories() {

spring-test/src/test/java/org/springframework/test/context/configuration/interfaces/ContextConfigurationTestInterface.java

@@ -28,7 +28,7 @@
 @ContextConfiguration(classes = Config.class)
 interface ContextConfigurationTestInterface {
 
-	static class Config {
+	class Config {
 
 		@Bean
 		Employee employee() {

spring-test/src/test/java/org/springframework/test/context/configuration/interfaces/WebAppConfigurationTestInterface.java

@@ -30,7 +30,7 @@
 interface WebAppConfigurationTestInterface {
 
 	@Configuration
-	static class Config {
+	class Config {
 		/* no user beans required for these tests */
 	}
 

spring-test/src/test/java/org/springframework/test/context/junit4/annotation/meta/ConfigClassesAndProfileResolverWithCustomDefaultsMetaConfig.java

@@ -52,7 +52,7 @@
 
 	@Configuration
 	@Profile("dev")
-	static class DevConfig {
+	class DevConfig {
 
 		@Bean
 		public String foo() {
@@ -62,7 +62,7 @@ public String foo() {
 
 	@Configuration
 	@Profile("prod")
-	static class ProductionConfig {
+	class ProductionConfig {
 
 		@Bean
 		public String foo() {
@@ -72,15 +72,15 @@ public String foo() {
 
 	@Configuration
 	@Profile("resolver")
-	static class ResolverConfig {
+	class ResolverConfig {
 
 		@Bean
 		public String foo() {
 			return "Resolver Foo";
 		}
 	}
 
-	static class CustomResolver implements ActiveProfilesResolver {
+	class CustomResolver implements ActiveProfilesResolver {
 
 		@Override
 		public String[] resolve(Class<?> testClass) {

spring-test/src/test/java/org/springframework/test/context/junit4/annotation/meta/ConfigClassesAndProfilesWithCustomDefaultsMetaConfig.java

@@ -50,7 +50,7 @@
 
 	@Configuration
 	@Profile("dev")
-	static class DevConfig {
+	class DevConfig {
 
 		@Bean
 		public String foo() {
@@ -60,7 +60,7 @@ public String foo() {
 
 	@Configuration
 	@Profile("prod")
-	static class ProductionConfig {
+	class ProductionConfig {
 
 		@Bean
 		public String foo() {

spring-test/src/test/java/org/springframework/test/context/junit4/rules/ProgrammaticTxMgmtSpringRuleTests.java

@@ -97,24 +97,11 @@ void beforeTransaction() {
 	void afterTransaction() {
 		String method = this.testName.getMethodName();
 		switch (method) {
-			case "commitTxAndStartNewTx":
-			case "commitTxButDoNotStartNewTx": {
-				assertUsers("Dogbert");
-				break;
-			}
-			case "rollbackTxAndStartNewTx":
-			case "rollbackTxButDoNotStartNewTx":
-			case "startTxWithExistingTransaction": {
-				assertUsers("Dilbert");
-				break;
-			}
-			case "rollbackTxAndStartNewTxWithDefaultCommitSemantics": {
-				assertUsers("Dilbert", "Dogbert");
-				break;
-			}
-			default: {
-				fail("missing 'after transaction' assertion for test method: " + method);
-			}
+			case "commitTxAndStartNewTx", "commitTxButDoNotStartNewTx" -> assertUsers("Dogbert");
+			case "rollbackTxAndStartNewTx", "rollbackTxButDoNotStartNewTx", "startTxWithExistingTransaction" ->
+					assertUsers("Dilbert");
+			case "rollbackTxAndStartNewTxWithDefaultCommitSemantics" -> assertUsers("Dilbert", "Dogbert");
+			default -> fail("missing 'after transaction' assertion for test method: " + method);
 		}
 	}