Add more tests

Need to use box patterns

src/main.rs

@@ -1,4 +1,4 @@
-#![feature(advanced_slice_patterns, slice_patterns)]
+#![feature(advanced_slice_patterns, slice_patterns, box_attributes, box_patterns)]
 
 extern crate simplerepl;
 

src/parser.rs

@@ -291,6 +291,9 @@ mod tests {
     #[test]
     fn parse_test() {
         parsetest!("a", [ASTNode::ExprNode(Expression::Variable(ref s))], s == "a");
+        parsetest!("a + b",
+            [ASTNode::ExprNode(Expression::BinExp(ref plus, box Expression::Variable(ref a), box Expression::Variable(ref b)))],
+            plus == "+" && a == "a" && b == "b");
     }
 
 }