[Tests] Fix edge case in ScriptedMetricAggregatorTests

An expected exception is only thrown when there are documents in the index
created in the test setup. Fixed the test by making sure there is at least one.

Closes #31307

server/src/test/java/org/elasticsearch/search/aggregations/metrics/scripted/ScriptedMetricAggregatorTests.java

@@ -118,7 +118,7 @@ public static void initMockScripts() {
         SCRIPTS.put("initScriptParams", params -> {
             Map<String, Object> agg = (Map<String, Object>) params.get("_agg");
             Integer initialValue = (Integer)params.get("initialValue");
-            ArrayList<Integer> collector = new ArrayList();
+            ArrayList<Integer> collector = new ArrayList<>();
             collector.add(initialValue);
             agg.put("collector", collector);
             return agg;
@@ -175,7 +175,6 @@ public void testNoDocs() throws IOException {
     /**
      * without combine script, the "_aggs" map should contain a list of the size of the number of documents matched
      */
-    @SuppressWarnings("unchecked")
     public void testScriptedMetricWithoutCombine() throws IOException {
         try (Directory directory = newDirectory()) {
             int numDocs = randomInt(100);
@@ -190,8 +189,11 @@ public void testScriptedMetricWithoutCombine() throws IOException {
                 ScriptedMetric scriptedMetric = search(newSearcher(indexReader, true, true), new MatchAllDocsQuery(), aggregationBuilder);
                 assertEquals(AGG_NAME, scriptedMetric.getName());
                 assertNotNull(scriptedMetric.aggregation());
+                @SuppressWarnings("unchecked")
                 Map<String, Object> agg = (Map<String, Object>) scriptedMetric.aggregation();
-                assertEquals(numDocs, ((List<Integer>) agg.get("collector")).size());
+                @SuppressWarnings("unchecked")
+                List<Integer> list = (List<Integer>) agg.get("collector");
+                assertEquals(numDocs, list.size());
             }
         }
     }
@@ -300,10 +302,9 @@ public void testSelfReferencingAggStateAfterInit() throws IOException {
         }
     }
 
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/31307")
     public void testSelfReferencingAggStateAfterMap() throws IOException {
         try (Directory directory = newDirectory()) {
-            Integer numDocs = randomInt(100);
+            Integer numDocs = randomIntBetween(1, 100);
             try (RandomIndexWriter indexWriter = new RandomIndexWriter(random(), directory)) {
                 for (int i = 0; i < numDocs; i++) {
                     indexWriter.addDocument(singleton(new SortedNumericDocValuesField("number", i)));