Add capability check for tests

Author: carlosdelest

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/expression/function/fulltext/KnnTests.java

@@ -11,6 +11,7 @@
 import com.carrotsearch.randomizedtesting.annotations.ParametersFactory;
 
 import org.elasticsearch.index.query.QueryBuilder;
+import org.elasticsearch.xpack.esql.action.EsqlCapabilities;
 import org.elasticsearch.xpack.esql.core.expression.Expression;
 import org.elasticsearch.xpack.esql.core.expression.FieldAttribute;
 import org.elasticsearch.xpack.esql.core.expression.Literal;
@@ -22,6 +23,7 @@
 import org.elasticsearch.xpack.esql.expression.function.vector.Knn;
 import org.elasticsearch.xpack.esql.io.stream.PlanStreamOutput;
 import org.elasticsearch.xpack.esql.optimizer.rules.physical.local.LucenePushdownPredicates;
+import org.junit.Before;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -46,6 +48,11 @@ public static Iterable<Object[]> parameters() {
         return parameterSuppliersFromTypedData(addFunctionNamedParams(testCaseSuppliers()));
     }
 
+    @Before
+    public void checkCapability() {
+        assumeTrue("KNN is not enabled", EsqlCapabilities.Cap.KNN_FUNCTION.isEnabled());
+    }
+
     private static List<TestCaseSupplier> testCaseSuppliers() {
         List<TestCaseSupplier> suppliers = new ArrayList<>();