Fix and unmute org.elasticsearch.script.StatsSummaryTests:testEqualsAndHashCode (elastic#115922)

This commit fixes and unmutes org.elasticsearch.script.StatsSummaryTests:testEqualsAndHashCode.

Previously, there was no guarantee that the doubles added to stats1 and stats2 will be different. In fact, the count may even be zero - which we seen in one particular failure. The simplest thing here, to avoid this potential situation, is to ensure that there is at least one value, and that the values added to each stats instance are different.

Author: ChrisHegarty

muted-tests.yml

@@ -103,9 +103,6 @@ tests:
 - class: org.elasticsearch.xpack.sql.qa.single_node.JdbcSqlSpecIT
   method: test {case-functions.testUcaseInline3}
   issue: https://github.com/elastic/elasticsearch/issues/112643
-- class: org.elasticsearch.script.StatsSummaryTests
-  method: testEqualsAndHashCode
-  issue: https://github.com/elastic/elasticsearch/issues/112439
 - class: org.elasticsearch.repositories.blobstore.testkit.analyze.HdfsRepositoryAnalysisRestIT
   issue: https://github.com/elastic/elasticsearch/issues/112889
 - class: org.elasticsearch.xpack.sql.qa.security.JdbcSqlSpecIT

server/src/test/java/org/elasticsearch/script/StatsSummaryTests.java

@@ -75,9 +75,21 @@ public void testEqualsAndHashCode() {
         assertThat(stats1, equalTo(stats2));
         assertThat(stats1.hashCode(), equalTo(stats2.hashCode()));
 
+        // Accumulators with same sum, but different counts are not equals
+        stats1.accept(1);
+        stats1.accept(1);
+        stats2.accept(2);
+        assertThat(stats1.getSum(), equalTo(stats2.getSum()));
+        assertThat(stats1.getCount(), not(equalTo(stats2.getCount())));
+        assertThat(stats1, not(equalTo(stats2)));
+        assertThat(stats1.hashCode(), not(equalTo(stats2.hashCode())));
+
         // Accumulators with different values are not equals
-        randomDoubles(randomIntBetween(0, 20)).forEach(stats1);
-        randomDoubles(randomIntBetween(0, 20)).forEach(stats2);
+        stats1.reset();
+        stats2.reset();
+        randomDoubles(randomIntBetween(1, 20)).forEach(stats1.andThen(v -> stats2.accept(v + randomDoubleBetween(0.0, 1.0, false))));
+        assertThat(stats1.getCount(), equalTo(stats2.getCount()));
+        assertThat(stats1.getSum(), not(equalTo(stats2.getSum())));
         assertThat(stats1, not(equalTo(stats2)));
         assertThat(stats1.hashCode(), not(equalTo(stats2.hashCode())));
     }