Add retry for flaky tests.

Author: nedtwigg

gradle/special-tests.gradle

@@ -1,14 +1,23 @@
+apply plugin: 'org.gradle.test-retry'
+
 def special = [
 	'Npm',
 	'Black',
 	'Clang'
 ]
 
+boolean isCiServer = true
 tasks.named('test') {
 	// See com.diffplug.spotless.tag package for available JUnit 5 @Tag annotations
 	useJUnitPlatform {
 		excludeTags special as String[]
 	}
+	if (isCiServer) {
+		retry {
+			maxRetries = 2
+			maxFailures = 2
+		}
+	}
 }
 
 special.forEach { tag ->

settings.gradle

@@ -9,6 +9,8 @@ pluginManagement {
 		id 'com.github.spotbugs'                   version '4.7.8'
 		// https://github.com/diffplug/spotless-changelog
 		id 'com.diffplug.spotless-changelog'       version '2.2.0'
+		// https://github.com/gradle/test-retry-gradle-plugin/releases
+		id 'org.gradle.test-retry'                 version '1.3.1'
 	}
 }
 plugins {
@@ -17,6 +19,7 @@ plugins {
 	id 'io.github.gradle-nexus.publish-plugin' apply false
 	id 'com.github.spotbugs'                   apply false
 	id 'com.diffplug.spotless-changelog'       apply false
+	id 'org.gradle.test-retry'                 apply false
 }
 if (System.env['CI'] != null) {
 	// use the remote buildcache on all CI builds