Fix test that assumed a certain order of doc IDs with equal score

If the score is equal in Lucene the order of the result depends on the
actual global doc ID such that due to background merges or concurrency
these test can return different result set orders.

src/test/java/org/elasticsearch/test/hamcrest/ElasticsearchAssertions.java

@@ -31,6 +31,8 @@
 import org.hamcrest.Matcher;
 
 import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
 
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.*;
@@ -46,6 +48,16 @@ public class ElasticsearchAssertions {
     public static void assertHitCount(SearchResponse searchResponse, long expectedHitCount) {
         assertThat(searchResponse.getHits().totalHits(), is(expectedHitCount));
     }
+
+    public static void assertSearchHits(SearchResponse searchResponse, String... ids) {
+        assertThat("Expected different hit count", searchResponse.getHits().hits().length, equalTo(ids.length));
+
+        Set<String> idsSet = new HashSet<String>(Arrays.asList(ids));
+        for (SearchHit hit : searchResponse.getHits()) {
+            assertThat("Expected id: " + hit.getId() + " in the result but wasn't", idsSet.remove(hit.getId()), equalTo(true));
+        }
+        assertThat("Expected ids: " + Arrays.toString(idsSet.toArray(new String[0])) + " in the result - result size differs", idsSet.size(), equalTo(0));
+    }
 
     public static void assertHitCount(CountResponse countResponse, long expectedHitCount) {
         assertThat(countResponse.getCount(), is(expectedHitCount));

src/test/java/org/elasticsearch/test/integration/search/query/SimpleQueryTests.java

@@ -39,13 +39,9 @@
 import static org.elasticsearch.common.xcontent.XContentFactory.jsonBuilder;
 import static org.elasticsearch.index.query.FilterBuilders.*;
 import static org.elasticsearch.index.query.QueryBuilders.*;
-import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertHitCount;
-import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertNoFailures;
-import static org.hamcrest.MatcherAssert.assertThat;
+import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.*;
 import static org.hamcrest.Matchers.anyOf;
 import static org.hamcrest.Matchers.equalTo;
-import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
 
 /**
  *
@@ -545,8 +541,8 @@ public void testMultiMatchQuery() throws Exception {
                 .execute().actionGet();
 
         assertThat(searchResponse.getHits().totalHits(), equalTo(2l));
-        assertThat("1", equalTo(searchResponse.getHits().getAt(0).id()));
-        assertThat("2", equalTo(searchResponse.getHits().getAt(1).id()));
+        // this uses dismax so scores are equal and the order can be arbitrary
+        assertSearchHits(searchResponse, "1", "2");
 
         builder.useDisMax(false);
         searchResponse = client().prepareSearch()