[test] Adding test case for nulls

- ensuring nulls work
- will be undone

lazy.go

@@ -103,11 +103,11 @@ func RandomGenerate(m Config) (*Mock, error) {
 				nullType := false
 				switch field.Type {
 				case reflect.TypeOf(sql.NullTime{}):
-					if isNull() {
+					// if isNull() {
 					rows[y] = append(rows[y], nil)
-					} else {
+					// } else {
-						rows[y] = append(rows[y], time.Now())
+					// 	rows[y] = append(rows[y], time.Now())
-					}
+					// }
 					nullType = true
 				case reflect.TypeOf(sql.NullInt16{}):
 					if isNull() {