Test Gradle plugin against Gradle 8.1

Closes gh-35034

Author: wilkinsona

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/plugin/KotlinPluginActionIntegrationTests.java

@@ -48,28 +48,31 @@ void noKotlinVersionPropertyWithoutKotlinPlugin() {
 
 	@TestTemplate
 	void kotlinVersionPropertyIsSet() {
-		String output = this.gradleBuild.build("kotlinVersion", "dependencies", "--configuration", "compileClasspath")
+		String output = this.gradleBuild.expectDeprecationWarningsWithAtLeastVersion("8.1-rc-1")
+			.build("kotlinVersion", "dependencies", "--configuration", "compileClasspath")
 			.getOutput();
 		assertThat(output).containsPattern("Kotlin version: [0-9]\\.[0-9]\\.[0-9]+");
 	}
 
 	@TestTemplate
 	void kotlinCompileTasksUseJavaParametersFlagByDefault() {
-		assertThat(this.gradleBuild.build("kotlinCompileTasksJavaParameters").getOutput())
-			.contains("compileKotlin java parameters: true")
+		assertThat(this.gradleBuild.expectDeprecationWarningsWithAtLeastVersion("8.1-rc-1")
+			.build("kotlinCompileTasksJavaParameters")
+			.getOutput()).contains("compileKotlin java parameters: true")
 			.contains("compileTestKotlin java parameters: true");
 	}
 
 	@TestTemplate
 	void kotlinCompileTasksCanOverrideDefaultJavaParametersFlag() {
-		assertThat(this.gradleBuild.build("kotlinCompileTasksJavaParameters").getOutput())
-			.contains("compileKotlin java parameters: false")
+		assertThat(this.gradleBuild.expectDeprecationWarningsWithAtLeastVersion("8.1-rc-1")
+			.build("kotlinCompileTasksJavaParameters")
+			.getOutput()).contains("compileKotlin java parameters: false")
 			.contains("compileTestKotlin java parameters: false");
 	}
 
 	@TestTemplate
 	void taskConfigurationIsAvoided() throws IOException {
-		BuildResult result = this.gradleBuild.build("help");
+		BuildResult result = this.gradleBuild.expectDeprecationWarningsWithAtLeastVersion("8.1-rc-1").build("help");
 		String output = result.getOutput();
 		BufferedReader reader = new BufferedReader(new StringReader(output));
 		String line;

spring-boot-project/spring-boot-tools/spring-boot-gradle-test-support/src/main/java/org/springframework/boot/testsupport/gradle/testkit/GradleVersions.java

@@ -34,15 +34,15 @@ private GradleVersions() {
 
 	public static List<String> allCompatible() {
 		if (isJava18()) {
-			return Arrays.asList("7.3.3", GradleVersion.current().getVersion(), "8.0.2");
+			return Arrays.asList("7.3.3", GradleVersion.current().getVersion(), "8.0.2", "8.1");
 		}
 		if (isJava17()) {
-			return Arrays.asList("7.2", GradleVersion.current().getVersion(), "8.0.2");
+			return Arrays.asList("7.2", GradleVersion.current().getVersion(), "8.0.2", "8.1");
 		}
 		if (isJava16()) {
-			return Arrays.asList("7.0.2", GradleVersion.current().getVersion(), "8.0.2");
+			return Arrays.asList("7.0.2", GradleVersion.current().getVersion(), "8.0.2", "8.1");
 		}
-		return Arrays.asList("6.8.3", "6.9.4", "7.0.2", GradleVersion.current().getVersion(), "8.0.2");
+		return Arrays.asList("6.8.3", "6.9.4", "7.0.2", GradleVersion.current().getVersion(), "8.0.2", "8.1");
 	}
 
 	public static String minimumCompatible() {