forgot to include Java attribute group tests

Author: mengxr

mllib/src/test/java/org/apache/spark/ml/attribute/JavaAttributeGroupSuite.java

@@ -0,0 +1,45 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.ml.attribute;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class JavaAttributeGroupSuite {
+
+  @Test
+  public void testAttributeGroup() {
+    Attribute[] attrs = new Attribute[]{
+      NumericAttribute.defaultAttr(),
+      NominalAttribute.defaultAttr(),
+      BinaryAttribute.defaultAttr().withIndex(0),
+      NumericAttribute.defaultAttr().withName("age").withSparsity(0.8),
+      NominalAttribute.defaultAttr().withName("size").withValues("small", "medium", "large"),
+      BinaryAttribute.defaultAttr().withName("clicked").withValues("no", "yes"),
+      NumericAttribute.defaultAttr(),
+      NumericAttribute.defaultAttr()
+    };
+    AttributeGroup group = new AttributeGroup("user", attrs);
+    Assert.assertEquals(8, group.size());
+    Assert.assertEquals("user", group.name());
+    Assert.assertEquals(NumericAttribute.defaultAttr().withIndex(0), group.getAttr(0));
+    Assert.assertEquals(3, group.indexOf("age"));
+    Assert.assertFalse(group.hasAttr("abc"));
+    Assert.assertEquals(group, AttributeGroup.fromStructField(group.toStructField()));
+  }
+}