Merge pull request #296 from eclipse/lb_flaky

Copied Flaky into .xtext.testing

org.eclipse.xtext.testing/src/org/eclipse/xtext/testing/Flaky.java

@@ -0,0 +1,95 @@
+/*******************************************************************************
+ * Copyright (c) 2014 itemis AG (http://www.itemis.eu) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *******************************************************************************/
+package org.eclipse.xtext.testing;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.junit.Assert;
+import org.junit.rules.TestRule;
+import org.junit.runner.Description;
+import org.junit.runners.model.Statement;
+
+import com.google.common.annotations.Beta;
+
+/**
+ * Annotate a method with {@code Flaky} to mark it as occasionally failing.
+ * 
+ * If the test class defines a {@code @Rule Flaky.Rule} (a public, non-static, initialized field),
+ * it will try to execute a flaky tests more than once if it failed. By default,
+ * three executions are tried.
+ * 
+ * @author Sebastian Zarnekow - Initial contribution and API
+ */
+@Beta
+@Documented
+@Target(ElementType.METHOD)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Flaky {
+
+	/**
+	 * The number of trials if the test method failed. Defaults to {@code 3}.
+	 */
+	int trials() default 3;
+	
+	/**
+	 * A test rule that will enable flaky tests to be executed more than once.
+	 */
+	class Rule implements TestRule {
+
+		@Override
+		public Statement apply(Statement base, Description description) {
+			Flaky flaky = description.getAnnotation(Flaky.class);
+			if (flaky == null) {
+				return base;
+			}
+			int trials = flaky.trials();
+			return new RepeatedStatement(base, trials);
+		}
+		
+		private static class RepeatedStatement extends Statement {
+
+			private final Statement base;
+			private final int trials;
+
+			public RepeatedStatement(Statement base, int trials) {
+				this.base = base;
+				this.trials = trials;
+			}
+
+			@Override
+			public void evaluate() throws Throwable {
+				if (trials <= 1 || trials > 100) {
+					throw new IllegalArgumentException("Illegal number of trials: " + trials + ", must be between 2 and 100 (inclusive)");
+				}
+				
+				int remaining = trials;
+				Throwable firstError = null;
+				while(remaining > 0) {
+					try {
+						base.evaluate();
+						return;
+					} catch(Throwable t) {
+						if (firstError == null) {
+							firstError = t;
+						}
+						remaining--;
+					}
+				}
+				Assert.assertNotNull(firstError);
+				throw firstError;
+			}
+			
+		}
+	}
+	
+	
+}