feat(tests): added constant test for bdd_from_expression

src/bdd/traits/from_expression.rs

@@ -65,7 +65,9 @@ fn try_from_rec<T: Debug + Clone + Ord>(
 mod tests {
     use super::*;
     use crate::traits::BooleanFunction;
+    use rstest::rstest;
     use std::str::FromStr;
+
     #[test]
     fn test_bdd_from_expression() {
         let exp_string = "(b | a & c & false) & !a | true".to_string();
@@ -79,6 +81,7 @@ mod tests {
 
         assert!(actual.is_equivalent(&expected))
     }
+
     #[test]
     fn test_bdd_from_expression_n_ary() {
         let exp_string = "(a | b | c) | (!a & !b & !c)".to_string();
@@ -92,4 +95,18 @@ mod tests {
 
         assert!(actual.is_equivalent(&expected))
     }
+
+    #[rstest]
+    fn test_bdd_from_expression_const(#[values("true", "false")] exp_string: &str) {
+        let input = Expression::from_str(exp_string).unwrap();
+        let actual = Bdd::try_from(input).unwrap();
+
+        let inputs = vec![];
+        let var_set = BddVariableSet::from(inputs.clone());
+        let inner_bdd = var_set.eval_expression_string(exp_string);
+        let expected = Bdd::new(inner_bdd, inputs);
+
+        assert!(actual.is_equivalent(&expected));
+        assert_eq!(actual, expected);
+    }
 }