Add NULL tests

Author: hvanhovell

sql/core/src/test/scala/org/apache/spark/sql/DataFrameWindowSuite.scala

@@ -292,4 +292,24 @@ class DataFrameWindowSuite extends QueryTest with SharedSQLContext {
         Row("b", 3, 8, 32),
         Row("b", 2, 4, 8)))
   }
+
+  test("null inputs") {
+    val df = Seq(("a", 1), ("a", 1), ("a", 2), ("a", 2), ("b", 4), ("b", 3), ("b", 2))
+      .toDF("key", "value")
+    val window = Window.orderBy()
+    checkAnswer(
+      df.select(
+        $"key",
+        $"value",
+        avg(lit(null)).over(window),
+        sum(lit(null)).over(window)),
+      Seq(
+        Row("a", 1, null, null),
+        Row("a", 1, null, null),
+        Row("a", 2, null, null),
+        Row("a", 2, null, null),
+        Row("b", 4, null, null),
+        Row("b", 3, null, null),
+        Row("b", 2, null, null)))
+  }
 }

sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/WindowQuerySuite.scala

@@ -227,4 +227,19 @@ class WindowQuerySuite extends QueryTest with SQLTestUtils with TestHiveSingleto
         Row("Manufacturer#5", "almond azure blanched chiffon midnight", 23, 315.9225931564038, 315.9225931564038, 46, 99807.08486666666, -0.9978877469246935, -5664.856666666666)))
       // scalastyle:on
   }
+
+  test("null arguments") {
+    checkAnswer(sql("""
+        |select  p_mfgr, p_name, p_size,
+        |sum(null) over(distribute by p_mfgr sort by p_name) as sum,
+        |avg(null) over(distribute by p_mfgr sort by p_name) as avg
+        |from part
+      """.stripMargin),
+      sql("""
+        |select  p_mfgr, p_name, p_size,
+        |null as sum,
+        |null as avg
+        |from part
+        """.stripMargin))
+  }
 }