Fix for DenseVectorFieldMapperTests to properly initialize random vector given the dimensions in mappings (#129912)

Author: pmpailis

muted-tests.yml

@@ -560,9 +560,6 @@ tests:
 - class: org.elasticsearch.xpack.rank.rrf.RRFRankClientYamlTestSuiteIT
   method: test {yaml=rrf/950_pinned_interaction/rrf with pinned retriever as a sub-retriever}
   issue: https://github.com/elastic/elasticsearch/issues/129845
-- class: org.elasticsearch.index.mapper.vectors.DenseVectorFieldMapperTests
-  method: testExistsQueryMinimalMapping
-  issue: https://github.com/elastic/elasticsearch/issues/129911
 - class: org.elasticsearch.xpack.test.rest.XPackRestIT
   method: test {p0=esql/60_usage/Basic ESQL usage output (telemetry) non-snapshot version}
   issue: https://github.com/elastic/elasticsearch/issues/129888
@@ -571,6 +568,7 @@ tests:
     extractedAssemble, #2]"
   issue: https://github.com/elastic/elasticsearch/issues/119871
 
+
 # Examples:
 #
 #  Mute a single test case in a YAML test suite:

server/src/test/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldMapperTests.java

@@ -65,6 +65,7 @@
 
 import static org.apache.lucene.codecs.lucene99.Lucene99HnswVectorsFormat.DEFAULT_BEAM_WIDTH;
 import static org.apache.lucene.codecs.lucene99.Lucene99HnswVectorsFormat.DEFAULT_MAX_CONN;
+import static org.apache.lucene.tests.index.BaseKnnVectorsFormatTestCase.randomNormalizedVector;
 import static org.elasticsearch.index.codec.vectors.IVFVectorsFormat.DYNAMIC_NPROBE;
 import static org.elasticsearch.index.mapper.vectors.DenseVectorFieldMapper.DEFAULT_OVERSAMPLE;
 import static org.elasticsearch.index.mapper.vectors.DenseVectorFieldMapper.IVF_FORMAT;
@@ -147,7 +148,17 @@ private void indexMapping(XContentBuilder b, IndexVersion indexVersion) throws I
 
     @Override
     protected Object getSampleValueForDocument() {
-        return elementType == ElementType.FLOAT ? List.of(0.5, 0.5, 0.5, 0.5) : List.of((byte) 1, (byte) 1, (byte) 1, (byte) 1);
+        return elementType == ElementType.FLOAT
+            ? convertToList(randomNormalizedVector(this.dims))
+            : List.of((byte) 1, (byte) 1, (byte) 1, (byte) 1);
+    }
+
+    private static List<Float> convertToList(float[] vector) {
+        List<Float> list = new ArrayList<>(vector.length);
+        for (float v : vector) {
+            list.add(v);
+        }
+        return list;
     }
 
     @Override