Mark filtered rows as true

We recently fixed the outcome of filtered rows and made them default to true instead of false, which was a bug earlier. This change maintains that behavior.

src/main/scala/com/amazon/deequ/constraints/Constraint.scala

@@ -960,7 +960,10 @@ object Constraint {
               case FilteredRowOutcome.TRUE => true
               case FilteredRowOutcome.NULL => null
             }
-          case None => null
+          // https://github.com/awslabs/deequ/issues/530
+          // Filtered rows should be marked as true by default.
+          // They can be set to null using the FilteredRowOutcome option.
+          case None => true
         }
       }
 

src/test/scala/com/amazon/deequ/VerificationSuiteTest.scala

@@ -371,11 +371,11 @@ class VerificationSuiteTest extends WordSpec with Matchers with SparkContextSpec
 
       // filtered rows 1, 2, 3 (where item > 3)
       val minRowLevel = resultData.select(expectedColumn4).collect().map(r => r.getAs[Any](0))
-      assert(Seq(null, null, null, true, true, true).sameElements(minRowLevel))
+      assert(Seq(true, true, true, true, true, true).sameElements(minRowLevel))
 
       // filtered rows 4, 5, 6 (where item < 4)
       val maxRowLevel = resultData.select(expectedColumn5).collect().map(r => r.getAs[Any](0))
-      assert(Seq(true, true, true, null, null, null).sameElements(maxRowLevel))
+      assert(Seq(true, true, true, true, true, true).sameElements(maxRowLevel))
 
       // filtered rows 4, 5, 6 (where item < 4)
       val rowLevel6 = resultData.select(expectedColumn6).collect().map(r => r.getAs[Any](0))