Raise the minimum supported version of Gradle to 8.14 and support 9.x

Closes gh-43573
Closes gh-43574

build-plugin/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/plugin/SpringBootPluginIntegrationTests.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2012-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.gradle.plugin;
+
+import org.gradle.testkit.runner.BuildResult;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.DisabledForJreRange;
+import org.junit.jupiter.api.condition.JRE;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import org.springframework.boot.gradle.testkit.PluginClasspathGradleBuild;
+import org.springframework.boot.testsupport.BuildOutput;
+import org.springframework.boot.testsupport.gradle.testkit.GradleBuild;
+import org.springframework.boot.testsupport.gradle.testkit.GradleBuildExtension;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Integration tests for {@link SpringBootPlugin}.
+ *
+ * @author Andy Wilkinson
+ */
+@ExtendWith(GradleBuildExtension.class)
+class SpringBootPluginIntegrationTests {
+
+	final GradleBuild gradleBuild = new PluginClasspathGradleBuild(new BuildOutput(getClass()));
+
+	@Test
+	@DisabledForJreRange(min = JRE.JAVA_24)
+	void failFastWithVersionOfGradle8LowerThanRequired() {
+		BuildResult result = this.gradleBuild.gradleVersion("8.13").buildAndFail();
+		assertThat(result.getOutput()).contains(
+				"Spring Boot plugin requires Gradle 8.x (8.14 or later) or 9.x. The current version is Gradle 8.13");
+	}
+
+}