Add tree walk eval test

schala-lang/language/src/tree_walk_eval/mod.rs

@@ -7,6 +7,8 @@ use std::fmt::Write;
 use std::rc::Rc;
 use std::convert::From;
 
+mod test;
+
 type EvalResult<T> = Result<T, String>;
 
 #[derive(Debug)]

schala-lang/language/src/tree_walk_eval/test.rs

@@ -0,0 +1,24 @@
+#![cfg(test)]
+
+use crate::symbol_table::SymbolTable;
+use crate::tree_walk_eval::State;
+
+fn evaluate_input(input: &str) -> Result<String, String> {
+  let ast = crate::util::quick_ast(input);
+  let mut symbol_table = SymbolTable::new();
+  symbol_table.process_ast(&ast).unwrap();
+  let reduced_ir = crate::reduced_ir::reduce(&ast, &symbol_table);
+  let mut state = State::new();
+  let mut outputs = state.evaluate(reduced_ir, true);
+  outputs.pop().unwrap()
+}
+
+fn eval_assert(input: &str, expected: &str) {
+    assert_eq!(evaluate_input(input), Ok(expected.to_string()));
+}
+
+#[test]
+fn test_basic_eval() {
+  eval_assert("1 + 2", "3");
+  //eval_assert("let mut a = 1; a = 2", "()");
+}