Add tests for optimized expression evaluation.

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/ExpressionEvaluationSuite.scala

@@ -108,9 +108,7 @@ class ExpressionEvaluationSuite extends FunSuite {
       truthTable.foreach {
         case (l,r,answer) =>
           val expr = op(Literal(l, BooleanType), Literal(r, BooleanType))
-          val result = expr.eval(null)
-          if (result != answer)
-            fail(s"$expr should not evaluate to $result, expected: $answer")
+          checkEvaluation(expr, answer)
       }
     }
   }

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/ExpressionOptimizationSuite.scala

@@ -0,0 +1,36 @@
+/*
+ * 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.sql.catalyst.optimizer
+
+import org.apache.spark.sql.catalyst.expressions._
+import org.apache.spark.sql.catalyst.plans.logical._
+
+/**
+ * Overrides our expression evaluation tests and reruns them after optimization has occured.  This
+ * is to ensure that constant folding and other optimizations do not break anything.
+ */
+class ExpressionOptimizationSuite extends ExpressionEvaluationSuite {
+  override def checkEvaluation(
+      expression: Expression,
+      expected: Any,
+      inputRow: Row = EmptyRow): Unit = {
+    val plan = Project(Alias(expression, s"Optimized($expression)")() :: Nil, NoRelation)
+    val optimizedPlan = Optimizer(plan)
+    super.checkEvaluation(optimizedPlan.expressions.head, expected, inputRow)
+  }
+}