[7.7][ML] Unmute classification cardinality integ test (#54165) (#54174)

Adjusts test to work for new cardinality limit.

Backport of #54165

Author: dimitris-athanasiou

x-pack/plugin/ml/qa/native-multi-node-tests/src/test/java/org/elasticsearch/xpack/ml/integration/ClassificationIT.java

@@ -349,23 +349,28 @@ public void testStopAndRestart() throws Exception {
         assertEvaluation(KEYWORD_FIELD, KEYWORD_FIELD_VALUES, "ml." + predictedClassField);
     }
 
-    @AwaitsFix(bugUrl = "Muted until ml-cpp supports multiple classes")
     public void testDependentVariableCardinalityTooHighError() throws Exception {
         initialize("cardinality_too_high");
         indexData(sourceIndex, 6, 5, KEYWORD_FIELD);
 
-        // Index one more document with a class different than the two already used.
-        client().execute(
-            IndexAction.INSTANCE,
-            new IndexRequest(sourceIndex).setRefreshPolicy(WriteRequest.RefreshPolicy.IMMEDIATE).source(KEYWORD_FIELD, "fox")).actionGet();
+        // Index enough documents to have more classes than the allowed limit
+        BulkRequestBuilder bulkRequestBuilder = client().prepareBulk().setRefreshPolicy(WriteRequest.RefreshPolicy.IMMEDIATE);
+        for (int i = 0; i < Classification.MAX_DEPENDENT_VARIABLE_CARDINALITY - 1; i++) {
+            IndexRequest indexRequest = new IndexRequest(sourceIndex).source(KEYWORD_FIELD, "fox-" + i);
+            bulkRequestBuilder.add(indexRequest);
+        }
+        BulkResponse bulkResponse = bulkRequestBuilder.get();
+        if (bulkResponse.hasFailures()) {
+            fail("Failed to index data: " + bulkResponse.buildFailureMessage());
+        }
 
         DataFrameAnalyticsConfig config = buildAnalytics(jobId, sourceIndex, destIndex, null, new Classification(KEYWORD_FIELD));
         registerAnalytics(config);
         putAnalytics(config);
 
         ElasticsearchStatusException e = expectThrows(ElasticsearchStatusException.class, () -> startAnalytics(jobId));
         assertThat(e.status().getStatus(), equalTo(400));
-        assertThat(e.getMessage(), equalTo("Field [keyword-field] must have at most [2] distinct values but there were at least [3]"));
+        assertThat(e.getMessage(), equalTo("Field [keyword-field] must have at most [30] distinct values but there were at least [31]"));
     }
 
     public void testDependentVariableCardinalityTooHighButWithQueryMakesItWithinRange() throws Exception {