diff --git a/src/run.rs b/src/run.rs
index d8f3b13..5f99450 100644
--- a/src/run.rs
+++ b/src/run.rs
@@ -84,3 +84,24 @@ impl Eval for Expression {
 		}
 	}
 }
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use crate::ast;
+
+	#[test]
+	fn test_consts() {
+		let mut scope = Scope::default();
+		assert_eq!(ast::Constant::Nil.eval(&mut scope), None);
+		assert_eq!(
+			ast::Constant::Boolean(true).eval(&mut scope),
+			Some(true.into())
+		);
+		assert_eq!(ast::Constant::Number(42).eval(&mut scope), Some(42.into()));
+		assert_eq!(
+			ast::Constant::String("foobar".into()).eval(&mut scope),
+			Some("foobar".into())
+		);
+	}
+}