Assert compare validity in VarBin compare tests (#3441)

Signed-off-by: Robert Kruszewski <[email protected]>

Author: robert3005

vortex-array/src/arrays/varbin/compute/compare.rs

@@ -142,6 +142,10 @@ mod test {
         .to_bool()
         .unwrap();
 
+        assert_eq!(
+            &result.validity_mask().unwrap().to_boolean_buffer(),
+            &BooleanBuffer::from_iter([true, false, true])
+        );
         assert_eq!(
             result.boolean_buffer(),
             &BooleanBuffer::from_iter([true, false, false])
@@ -163,6 +167,10 @@ mod test {
             .to_bool()
             .unwrap();
 
+        assert_eq!(
+            &result.validity_mask().unwrap().to_boolean_buffer(),
+            &BooleanBuffer::from_iter([false, false, true])
+        );
         assert_eq!(
             result.boolean_buffer(),
             &BooleanBuffer::from_iter([false, true, true])