fix testJVectorKnnIndex_simpleCase (#692) (#693)

* chore: fix flaky testJVectorKnnIndex_simpleCase test



* doc: update changelog



---------



(cherry picked from commit 65c0eef)

Signed-off-by: ergun-kezer <ergun.kezer@ibm.com>
Signed-off-by: opensearch-ci-bot <opensearch-infra@amazon.com>
Co-authored-by: Ergün Kezer <ergkezer@gmail.com>
Co-authored-by: ergun-kezer <ergun.kezer@ibm.com>

Author: 3 people

CHANGELOG.md

@@ -11,6 +11,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ### Bug Fixes
 - Fix flaky testJVectorKnnIndex_filter_maxInnerProduct test case [681](https://github.com/opensearch-project/opensearch-jvector/pull/681)
+- Fix flaky testJVectorKnnIndex_simpleCase  test case [692](https://github.com/opensearch-project/opensearch-jvector/pull/692)
 
 ### Infrastructure
 ### Documentation

src/test/java/org/opensearch/knn/index/codec/jvector/KNNJVectorTests.java

@@ -94,7 +94,7 @@ public void testJVectorKnnIndex_simpleCase() throws IOException {
             try (IndexReader reader = DirectoryReader.open(w)) {
                 int expectedNumOfSegments = indexWriterConfig.getMaxBufferedDocs() < 0 ? 1
                     : totalNumberOfDocs > indexWriterConfig.getMaxBufferedDocs()
-                        ? totalNumberOfDocs / indexWriterConfig.getMaxBufferedDocs() + 1
+                        ? Math.ceilDiv(totalNumberOfDocs, indexWriterConfig.getMaxBufferedDocs())
                     : 1;
                 log.info("We should now have a {} segment(s) with 10 documents", expectedNumOfSegments);
                 Assert.assertEquals(expectedNumOfSegments, reader.getContext().leaves().size());