Add property for evaluating numbers

1 files changed, 10 insertions, 6 deletions

diff --git a/rust/src/lambda.rs b/rust/src/lambda.rs
index a24b031..3c1c8b6 100644
--- a/rust/src/lambda.rs
+++ b/rust/src/lambda.rs
@@ -23,18 +23,22 @@ impl Display for Value {
     }
 }
 
-fn interpret(_arg: &str) -> Value {
-    Value::Num(1)
+fn interpret(arg: &str) -> Value {
+    Value::Num(arg.parse().unwrap())
 }
 
 #[cfg(test)]
 mod tests {
     use super::interpret;
     use super::Value::Num;
+    // Bring the macros and other important things into scope.
+    use proptest::prelude::*;
 
-    #[test]
-    fn it_works() {
-        let result = interpret("1");
-        assert_eq!(Num(1), result);
+    proptest! {
+        #[test]
+        fn interpret_integer_as_number(i in -1000i32..1000) {
+            let result = interpret(&i.to_string());
+            assert_eq!(Num(i), result);
+        }
     }
 }