Configure Gradle's Test Retry plugin

Closes gh-20144

buildSrc/build.gradle

@@ -20,6 +20,7 @@ dependencies {
 	implementation("org.apache.maven:maven-embedder:3.6.2")
 	implementation("org.asciidoctor:asciidoctor-gradle-jvm:3.0.0")
 	implementation("org.asciidoctor:asciidoctor-gradle-jvm-pdf:3.0.0")
+	implementation("org.gradle:test-retry-gradle-plugin:1.1.3")
 	implementation("org.springframework:spring-core:5.2.2.RELEASE")
 	implementation("org.springframework:spring-web:5.2.2.RELEASE")
 	implementation("com.google.code.gson:gson:2.8.5")

buildSrc/src/main/java/org/springframework/boot/build/ConventionsPlugin.java

@@ -56,6 +56,8 @@ import org.gradle.api.tasks.bundling.Jar;
 import org.gradle.api.tasks.compile.JavaCompile;
 import org.gradle.api.tasks.javadoc.Javadoc;
 import org.gradle.api.tasks.testing.Test;
+import org.gradle.testretry.TestRetryPlugin;
+import org.gradle.testretry.TestRetryTaskExtension;
 
 import org.springframework.boot.build.testing.TestFailuresPlugin;
 import org.springframework.util.FileCopyUtils;
@@ -71,7 +73,8 @@ import org.springframework.util.FileCopyUtils;
  * <ul>
  * <li>{@code sourceCompatibility} is set to {@code 1.8}
  * <li>{@link SpringJavaFormatPlugin Spring Java Format}, {@link CheckstylePlugin
- * Checkstyle}, and {@link TestFailuresPlugin Test Failures} plugins are applied
+ * Checkstyle}, {@link TestFailuresPlugin Test Failures}, and {@link TestRetryPlugin Test
+ * Retry} plugins are applied
  * <li>{@link Test} tasks are configured to use JUnit Platform and use a max heap of 1024M
  * <li>{@link JavaCompile}, {@link Javadoc}, and {@link FormatTask} tasks are configured
  * to use UTF-8 encoding
@@ -139,10 +142,16 @@ public class ConventionsPlugin implements Plugin<Project> {
 				javadoc.getOptions().source("1.8").encoding("UTF-8");
 				withOptionalBuildJavaHome(project, (javaHome) -> javadoc.setExecutable(javaHome + "/bin/javadoc"));
 			});
+			project.getPlugins().apply(TestRetryPlugin.class);
 			project.getTasks().withType(Test.class, (test) -> {
 				withOptionalBuildJavaHome(project, (javaHome) -> test.setExecutable(javaHome + "/bin/java"));
 				test.useJUnitPlatform();
 				test.setMaxHeapSize("1024M");
+				project.getPlugins().withType(TestRetryPlugin.class, (testRetryPlugin) -> {
+					TestRetryTaskExtension testRetry = test.getExtensions().getByType(TestRetryTaskExtension.class);
+					testRetry.getFailOnPassedAfterRetry().set(true);
+					testRetry.getMaxRetries().set(3);
+				});
 			});
 			project.getTasks().withType(Jar.class, (jar) -> {
 				project.afterEvaluate((evaluated) -> {

buildSrc/src/test/java/org/springframework/boot/build/ConventionsPluginTests.java

@@ -24,6 +24,7 @@ import java.io.PrintWriter;
 import java.util.jar.JarEntry;
 import java.util.jar.JarFile;
 
+import org.gradle.testkit.runner.BuildResult;
 import org.gradle.testkit.runner.GradleRunner;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -74,8 +75,29 @@ class ConventionsPluginTests {
 		}
 	}
 
-	private void runGradle(String... args) {
-		GradleRunner.create().withProjectDir(this.projectDir).withArguments(args).withPluginClasspath().build();
+	@Test
+	void testRetryIsConfigured() throws IOException {
+		try (PrintWriter out = new PrintWriter(new FileWriter(this.buildFile))) {
+			out.println("plugins {");
+			out.println("    id 'java'");
+			out.println("    id 'org.springframework.boot.conventions'");
+			out.println("}");
+			out.println("description 'Test'");
+			out.println("task retryConfig {");
+			out.println("    doLast {");
+			out.println("    test.retry {");
+			out.println("            println \"maxRetries: ${maxRetries.get()}\"");
+			out.println("            println \"failOnPassedAfterRetry: ${failOnPassedAfterRetry.get()}\"");
+			out.println("        }");
+			out.println("    }");
+			out.println("}");
+		}
+		assertThat(runGradle("retryConfig", "--stacktrace").getOutput()).contains("maxRetries: 3")
+				.contains("failOnPassedAfterRetry: true");
+	}
+
+	private BuildResult runGradle(String... args) {
+		return GradleRunner.create().withProjectDir(this.projectDir).withArguments(args).withPluginClasspath().build();
 	}
 
 }