Add a RepeatRule to help repeating flaky tests

A JUnit TestRule which enables to run the same JUnit test repeatedly.
This may help to identify the root cause why a flaky tests which succeed
most often does fail sometimes.

Add the RepeatRule to the test class containing the test to be repeated:

public class MyTest {
	@Rule
	public RepeatRule repeatRule = new RepeatRule();
	...
}
 
and annotate the test to be repeated with the @Repeat(n=<repetitions>)
annotation:
 
	@Test
	@Repeat(n = 100)
	public void test() {
		...
	}
 
then this test will be repeated 100 times. If any test execution fails
test repetition will be stopped.

Change-Id: I7c49ccebe1cb00bcde6b002b522d95c13fd3a35e
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.junit/META-INF/MANIFEST.MF

@@ -21,7 +21,10 @@ Import-Package: org.eclipse.jgit.api;version="[4.5.0,4.6.0)",
  org.eclipse.jgit.treewalk.filter;version="[4.5.0,4.6.0)",
  org.eclipse.jgit.util;version="[4.5.0,4.6.0)",
  org.eclipse.jgit.util.io;version="[4.5.0,4.6.0)",
- org.junit;version="[4.0.0,5.0.0)"
+ org.junit;version="[4.0.0,5.0.0)",
+ org.junit.rules;version="[4.9.0,5.0.0)",
+ org.junit.runner;version="[4.0.0,5.0.0)",
+ org.junit.runners.model;version="[4.5.0,5.0.0)"
 Export-Package: org.eclipse.jgit.junit;version="4.5.0";
   uses:="org.eclipse.jgit.dircache,
    org.eclipse.jgit.lib,

org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/Repeat.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2016, Matthias Sohn <matthias.sohn@sap.com>
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.eclipse.jgit.junit;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ java.lang.annotation.ElementType.METHOD })
+public @interface Repeat {
+	public abstract int n();
+}

org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/RepeatRule.java

@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2016, Matthias Sohn <matthias.sohn@sap.com>
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.eclipse.jgit.junit;
+
+import java.text.MessageFormat;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+import org.junit.rules.TestRule;
+import org.junit.runner.Description;
+import org.junit.runners.model.Statement;
+
+/**
+ * {@link TestRule} which enables to run the same JUnit test repeatedly. Add
+ * this rule to the test class
+ *
+ * <pre>
+ * public class MyTest {
+ * 	&#64;Rule
+ * 	public RepeatRule repeatRule = new RepeatRule();
+ * 	...
+ * }
+ * </pre>
+ *
+ * and annotate the test to be repeated with the
+ * {@code @Repeat(n=<repetitions>)} annotation
+ *
+ * <pre>
+ * &#64;Test
+ * &#64;Repeat(n = 100)
+ * public void test() {
+ * 	...
+ * }
+ * </pre>
+ *
+ * then this test will be repeated 100 times. If any test execution fails test
+ * repetition will be stopped.
+ */
+public class RepeatRule implements TestRule {
+
+	private static Logger LOG = Logger
+			.getLogger(RepeatRule.class.getName());
+
+	public static class RepeatedTestException extends RuntimeException {
+		private static final long serialVersionUID = 1L;
+
+		public RepeatedTestException(String message, Throwable cause) {
+			super(message, cause);
+		}
+	}
+
+	private static class RepeatStatement extends Statement {
+
+		private final int repetitions;
+
+		private final Statement statement;
+
+		private RepeatStatement(int repetitions, Statement statement) {
+			this.repetitions = repetitions;
+			this.statement = statement;
+		}
+
+		@Override
+		public void evaluate() throws Throwable {
+			for (int i = 0; i < repetitions; i++) {
+				try {
+					statement.evaluate();
+				} catch (Throwable e) {
+					RepeatedTestException ex = new RepeatedTestException(
+							MessageFormat.format(
+									"Repeated test failed when run for the {0}. time",
+									Integer.valueOf(i + 1)),
+							e);
+					LOG.log(Level.SEVERE, ex.getMessage(), ex);
+					throw ex;
+				}
+			}
+		}
+	}
+
+	@Override
+	public Statement apply(Statement statement, Description description) {
+		Statement result = statement;
+		Repeat repeat = description.getAnnotation(Repeat.class);
+		if (repeat != null) {
+			int n = repeat.n();
+			result = new RepeatStatement(n, statement);
+		}
+		return result;
+	}
+}