From 9040a96daf5e052556ec7140d3fbb03f1ece1b4f Mon Sep 17 00:00:00 2001
From: Yannick Welsch <yannick@welsch.lu>
Date: Wed, 9 Jan 2019 09:32:24 +0100
Subject: [PATCH] Zen2: Add test that checks that CoordinatorTests are
 reproducible (#37225)

Ensures reproducibility of the tests in CoordinatorTests.
---
 .../coordination/CoordinatorTests.java        | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/server/src/test/java/org/elasticsearch/cluster/coordination/CoordinatorTests.java b/server/src/test/java/org/elasticsearch/cluster/coordination/CoordinatorTests.java
index 17bf36b411b..a264015261d 100644
--- a/server/src/test/java/org/elasticsearch/cluster/coordination/CoordinatorTests.java
+++ b/server/src/test/java/org/elasticsearch/cluster/coordination/CoordinatorTests.java
@@ -18,6 +18,7 @@
  */
 package org.elasticsearch.cluster.coordination;
 
+import com.carrotsearch.randomizedtesting.RandomizedContext;
 import org.apache.logging.log4j.CloseableThreadContext;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -70,6 +71,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
+import java.util.concurrent.Callable;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Consumer;
 import java.util.function.Function;
@@ -128,6 +130,24 @@ public class CoordinatorTests extends ESTestCase {
         resetPortCounter();
     }
 
+    // check that runRandomly leads to reproducible results
+    public void testRepeatableTests() throws Exception {
+        final Callable<Long> test = () -> {
+            final Cluster cluster = new Cluster(randomIntBetween(1, 5));
+            cluster.runRandomly();
+            final long afterRunRandomly = value(cluster.getAnyNode().getLastAppliedClusterState());
+            cluster.stabilise();
+            final long afterStabilisation = value(cluster.getAnyNode().getLastAppliedClusterState());
+            return afterRunRandomly ^ afterStabilisation;
+        };
+        final long seed = randomLong();
+        logger.info("First run with seed [{}]", seed);
+        final long result1 = RandomizedContext.current().runWithPrivateRandomness(seed, test);
+        logger.info("Second run with seed [{}]", seed);
+        final long result2 = RandomizedContext.current().runWithPrivateRandomness(seed, test);
+        assertEquals(result1, result2);
+    }
+
     public void testCanUpdateClusterStateAfterStabilisation() {
         final Cluster cluster = new Cluster(randomIntBetween(1, 5));
         cluster.runRandomly();