add a test for SPARK-6660

Author: mengxr

python/pyspark/mllib/tests.py

@@ -36,6 +36,7 @@
 else:
     import unittest
 
+from pyspark.mllib.common import _to_java_object_rdd
 from pyspark.mllib.linalg import Vector, SparseVector, DenseVector, VectorUDT, _convert_to_vector,\
     DenseMatrix, Vectors, Matrices
 from pyspark.mllib.regression import LabeledPoint
@@ -634,6 +635,13 @@ def test_idf_model(self):
         idf = model.idf()
         self.assertEqual(len(idf), 11)
 
+
+class SerDeTest(PySparkTestCase):
+    def test_to_java_object_rdd(self):  # SPARK-6660
+        data = RandomRDDs.uniformRDD(self.sc, 10, 5, seed=0L)
+        self.assertEqual(_to_java_object_rdd(data).count(), 10)
+
+
 if __name__ == "__main__":
     if not _have_scipy:
         print "NOTE: Skipping SciPy tests as it does not seem to be installed"