Add tests

Author: carlosdelest

server/src/main/java/org/elasticsearch/search/vectors/RescoreVectorBuilder.java

@@ -24,7 +24,7 @@
 public class RescoreVectorBuilder implements Writeable, ToXContentObject {
 
     public static final ParseField OVERSAMPLE_FIELD = new ParseField("oversample");
-    public static final int MIN_OVERSAMPLE = 1;
+    public static final float MIN_OVERSAMPLE = 1.0F;
     private static final ConstructingObjectParser<RescoreVectorBuilder, Void> PARSER = new ConstructingObjectParser<>(
         "rescore",
         args -> new RescoreVectorBuilder((Float) args[0])

server/src/test/java/org/elasticsearch/search/vectors/KnnSearchBuilderTests.java

@@ -254,6 +254,14 @@ public void testInvalidK() {
         assertThat(e.getMessage(), containsString("[k] must be greater than 0"));
     }
 
+    public void testInvalidRescoreVectorBuilder() {
+        IllegalArgumentException e = expectThrows(
+            IllegalArgumentException.class,
+            () -> new KnnSearchBuilder("field", randomVector(3), 0, 100, new RescoreVectorBuilder(1.0F), null)
+        );
+        assertThat(e.getMessage(), containsString("[oversample] must be > 1.0"));
+    }
+
     public void testRewrite() throws Exception {
         float[] expectedArray = randomVector(randomIntBetween(10, 1024));
         RescoreVectorBuilder expectedRescore = new RescoreVectorBuilder(randomFloatBetween(1.0f, 10.0f, false));