Make some unit tests for the lexer

src/lexer/mod.rs

@@ -170,3 +170,25 @@ impl Iterator for Lexer {
         lex
     }
 }
+
+//
+// TESTING
+//
+
+#[test]
+fn lexer_finds_parens() {
+    let mut lexer = Lexer::new("()".to_string());
+    assert_next_token(&mut lexer, &Token::LeftParen("(".to_string()));
+    assert_next_token(&mut lexer, &Token::RightParen(")".to_string()));
+}
+
+#[test]
+fn lexer_finds_identifiers() {
+    let mut lexer = Lexer::new("abc".to_string());
+    assert_next_token(&mut lexer, &Token::Identifier("abc".to_string()));
+}
+
+fn assert_next_token(lexer: &mut Lexer, expected: &Token) {
+    let lex = lexer.next().unwrap();
+    assert_eq!(lex.token, *expected);
+}

src/lexer/token.rs

@@ -3,6 +3,7 @@
  */
 
 #[derive(Debug)]
+#[derive(PartialEq)]
 pub enum Token {
     LeftParen(String),
     RightParen(String),
@@ -15,7 +16,7 @@ pub enum Token {
 /// place.
 #[derive(Debug)]
 pub struct Lex {
-    token: Token,
+    pub token: Token,
 }
 
 impl Lex {