Add parser tests

src/parser/mod.rs

@@ -6,6 +6,9 @@ use std::vec::IntoIter;
 
 mod node_type;
 
+#[cfg(test)]
+mod tests;
+
 pub struct Parser {
     tokens: Peekable<IntoIter<Token>>,
     peeked: Vec<Token>,
@@ -108,7 +111,7 @@ impl Parser {
         let globals = Vec::new();
 
         while self.has_more() {
-            functions.push(self.parse_function().expect("Failed to parse function"))
+            functions.push(self.parse_function()?)
         }
 
         Ok(Program {

src/parser/tests.rs

@@ -0,0 +1,56 @@
+use crate::lexer::*;
+use crate::parser::*;
+
+#[test]
+fn test_parse_empty_function() {
+    let tokens = tokenize("fn main() {}");
+    let tree = parse(tokens);
+    assert!(tree.is_ok())
+}
+
+#[test]
+fn test_parse_function_with_return() {
+    let raw = "
+    fn main() {
+        return 1;
+    }
+    ";
+    let tokens = tokenize(raw);
+    let tree = parse(tokens);
+    assert!(tree.is_ok())
+}
+
+#[test]
+fn test_parse_missing_semicolon() {
+    let raw = "
+    fn main() {
+        return 1
+    }
+    ";
+    let tokens = tokenize(raw);
+    let tree = parse(tokens);
+    assert!(tree.is_err())
+}
+
+#[test]
+fn test_parse_no_function_context() {
+    let raw = "
+    let x = 1;
+    ";
+    let tokens = tokenize(raw);
+    let tree = parse(tokens);
+    assert!(tree.is_err())
+}
+
+#[test]
+fn test_parse_variable_declaration() {
+    let raw = "
+    fn main() {
+        let x = 1;
+        return x;
+    }
+    ";
+    let tokens = tokenize(raw);
+    let tree = parse(tokens);
+    assert!(tree.is_ok())
+}