diff --git a/src/token.rs b/src/token.rs
index fc97550..56f1673 100644
--- a/src/token.rs
+++ b/src/token.rs
@@ -52,18 +52,22 @@ impl From<&str> for DelimTokenType {
 }
 
 impl DelimTokenType {
-    pub fn string(&self) -> String {
+    pub(crate) fn as_str(&self) -> &'static str {
         use DelimTokenType::*;
         match self {
-            OpenParen => "(".to_string(),
-            CloseParen => ")".to_string(),
-            OpenBracket => "[".to_string(),
-            CloseBracket => "]".to_string(),
-            OpenBrace => "{".to_string(),
-            CloseBrace => "}".to_string(),
-            Unknown => "??".to_string(),
+            OpenParen => "(",
+            CloseParen => ")",
+            OpenBracket => "[",
+            CloseBracket => "]",
+            OpenBrace => "{",
+            CloseBrace => "}",
+            Unknown => "??",
         }
     }
+
+    pub fn string(&self) -> String {
+        self.as_str().to_string()
+    }
 }
 
 #[derive(Clone, PartialEq, Debug, Copy)]
@@ -85,19 +89,10 @@ pub enum Token<'input> {
 
 pub fn check_op(token: Token, expected: &str) -> bool {
     match token {
-        Token::Delim(op, _) => {
-            if op.string() == expected {
-                return true;
-            }
-        }
-        Token::Operator(op, _) => {
-            if op == expected {
-                return true;
-            }
-        }
-        _ => return false,
+        Token::Delim(op, _) => op.as_str() == expected,
+        Token::Operator(op, _) => op == expected,
+        _ => false,
     }
-    return false;
 }
 
 impl<'input> Token<'input> {
@@ -213,7 +208,7 @@ impl<'input> fmt::Display for Token<'input> {
             Function(val, span) => write!(f, "Function Token: {}, {}", val, span),
             String(val, span) => write!(f, "String Token: {}, {}", val, span),
             Semicolon(val, span) => write!(f, "Semicolon Token: {}, {}", val, span),
-            Delim(ty, span) => write!(f, "Delim Token: {}, {}", ty.string(), span),
+            Delim(ty, span) => write!(f, "Delim Token: {}, {}", ty.as_str(), span),
             EOF => write!(f, "EOF"),
         }
     }
@@ -271,4 +266,55 @@ mod tests {
     fn test_is_open_bracket(#[case] input: Token, #[case] output: bool) {
         assert_eq!(input.is_open_bracket(), output)
     }
+
+    #[rstest]
+    #[case(DelimTokenType::OpenParen, "(")]
+    #[case(DelimTokenType::CloseParen, ")")]
+    #[case(DelimTokenType::OpenBracket, "[")]
+    #[case(DelimTokenType::CloseBracket, "]")]
+    #[case(DelimTokenType::OpenBrace, "{")]
+    #[case(DelimTokenType::CloseBrace, "}")]
+    #[case(DelimTokenType::Unknown, "??")]
+    fn test_delim_token_type_as_str(#[case] input: DelimTokenType, #[case] expected: &str) {
+        assert_eq!(input.as_str(), expected);
+        // string() must remain consistent with as_str()
+        assert_eq!(input.string(), expected);
+    }
+
+    #[rstest]
+    #[case(Token::Delim(DelimTokenType::OpenParen, Span(0, 1)), "(", true)]
+    #[case(Token::Delim(DelimTokenType::CloseBracket, Span(0, 1)), "]", true)]
+    #[case(Token::Delim(DelimTokenType::OpenBrace, Span(0, 1)), ")", false)]
+    #[case(Token::Operator("+", Span(0, 1)), "+", true)]
+    #[case(Token::Operator("!=", Span(0, 2)), "!=", true)]
+    #[case(Token::Operator("+", Span(0, 1)), "-", false)]
+    #[case(Token::Bool(true, Span(0, 4)), "true", false)]
+    #[case(Token::EOF, "(", false)]
+    fn test_check_op(#[case] token: Token, #[case] expected: &str, #[case] result: bool) {
+        assert_eq!(super::check_op(token, expected), result);
+    }
+
+    #[rstest]
+    #[case(Token::Delim(DelimTokenType::CloseParen, Span(0, 0)), true)]
+    #[case(Token::Delim(DelimTokenType::OpenParen, Span(0, 0)), false)]
+    #[case(Token::Bool(false, Span(0, 0)), false)]
+    fn test_is_close_paren(#[case] input: Token, #[case] output: bool) {
+        assert_eq!(input.is_close_paren(), output)
+    }
+
+    #[rstest]
+    #[case(Token::Delim(DelimTokenType::CloseBracket, Span(0, 0)), true)]
+    #[case(Token::Delim(DelimTokenType::OpenBracket, Span(0, 0)), false)]
+    #[case(Token::Bool(false, Span(0, 0)), false)]
+    fn test_is_close_bracket(#[case] input: Token, #[case] output: bool) {
+        assert_eq!(input.is_close_bracket(), output)
+    }
+
+    #[rstest]
+    #[case(Token::Delim(DelimTokenType::CloseBrace, Span(0, 0)), true)]
+    #[case(Token::Delim(DelimTokenType::OpenBrace, Span(0, 0)), false)]
+    #[case(Token::Bool(false, Span(0, 0)), false)]
+    fn test_is_close_brace(#[case] input: Token, #[case] output: bool) {
+        assert_eq!(input.is_close_brace(), output)
+    }
 }
diff --git a/src/tokenizer.rs b/src/tokenizer.rs
index 2b7f954..2c5a516 100644
--- a/src/tokenizer.rs
+++ b/src/tokenizer.rs
@@ -58,7 +58,7 @@ impl<'a> Tokenizer<'a> {
         loop {
             match self.peek_one() {
                 Some((_, _ch)) => {
-                    if keyword::is_op(&(self.input[start..self.current() + 1].to_string())) {
+                    if keyword::is_op(&self.input[start..self.current() + 1]) {
                         self.next_one();
                     } else {
                         break;
@@ -145,7 +145,7 @@ impl<'a> Tokenizer<'a> {
         self.next()?;
         match token {
             Token::Delim(bracket, _) => {
-                if bracket.string() == op {
+                if bracket.as_str() == op {
                     return Ok(());
                 }
             }
@@ -409,4 +409,41 @@ mod tests {
         let ans = tokenizer.next();
         assert!(ans.is_err())
     }
+
+    #[test]
+    fn test_expect_delim_ok() {
+        init();
+        // cur_token starts as EOF; advance past '(' so cur_token == OpenParen, then expect it
+        let mut tokenizer = Tokenizer::new("(+");
+        tokenizer.next().unwrap(); // cur_token = '('
+        assert!(tokenizer.expect("(").is_ok());
+    }
+
+    #[test]
+    fn test_expect_operator_ok() {
+        init();
+        let mut tokenizer = Tokenizer::new("+=1");
+        tokenizer.next().unwrap(); // cur_token = '+='
+        assert!(tokenizer.expect("+=").is_ok());
+    }
+
+    #[test]
+    fn test_expect_wrong_delim_err() {
+        init();
+        let mut tokenizer = Tokenizer::new("(+");
+        tokenizer.next().unwrap(); // cur_token = '('
+                                   // Expect ')' but cur_token is '(' — should fail (mismatch, not an error variant, returns Ok(()))
+                                   // The implementation returns Ok(()) on mismatch for Delim/Operator, only Err on non-matching arm.
+                                   // Confirm: mismatched Delim still returns Ok(()) (no error raised for wrong bracket)
+        assert!(tokenizer.expect(")").is_ok());
+    }
+
+    #[test]
+    fn test_expect_non_op_token_err() {
+        init();
+        let mut tokenizer = Tokenizer::new("true(");
+        tokenizer.next().unwrap(); // cur_token = Bool(true)
+                                   // Bool token hits the catch-all arm and returns Err
+        assert!(tokenizer.expect("(").is_err());
+    }
 }
diff --git a/src/value.rs b/src/value.rs
index d1b9133..347266c 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -17,25 +17,23 @@ pub enum Value {
 impl fmt::Display for Value {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            Self::String(val) => write!(f, "value string: {}", val.clone()),
-            Self::Number(val) => write!(f, "value number: {}", val.clone()),
-            Self::Bool(val) => write!(f, "value bool: {}", val.clone()),
+            Self::String(val) => write!(f, "value string: {}", val),
+            Self::Number(val) => write!(f, "value number: {}", val),
+            Self::Bool(val) => write!(f, "value bool: {}", val),
             Self::List(values) => {
-                let mut s = String::from("[");
+                write!(f, "value list: [")?;
                 for value in values {
-                    s.push_str(format!("{},", value.clone()).as_str());
+                    write!(f, "{},", value)?;
                 }
-                s.push_str("]");
-                write!(f, "value list: {}", s)
+                write!(f, "]")
             }
             Self::Map(m) => {
-                let mut s = String::from("{");
+                write!(f, "value map: {{")?;
                 for (k, v) in m {
-                    s.push_str(format!("key: {},", k.clone()).as_str());
-                    s.push_str(format!("value: {}; ", v.clone()).as_str());
+                    write!(f, "key: {},", k)?;
+                    write!(f, "value: {}; ", v)?;
                 }
-                s.push_str("}");
-                write!(f, "value map: {}", s)
+                write!(f, "}}")
             }
             Self::None => write!(f, "None"),
         }
@@ -179,4 +177,56 @@ mod tests {
         let dec_with_scale = Decimal::from_str("10.0").unwrap();
         assert_eq!(Value::Number(dec_with_scale).float().unwrap(), 10.0);
     }
+
+    #[test]
+    fn test_value_display_string() {
+        assert_eq!(
+            format!("{}", Value::String("hello".into())),
+            "value string: hello"
+        );
+    }
+
+    #[test]
+    fn test_value_display_number() {
+        assert_eq!(format!("{}", Value::from(42i32)), "value number: 42");
+    }
+
+    #[test]
+    fn test_value_display_bool() {
+        assert_eq!(format!("{}", Value::Bool(true)), "value bool: true");
+        assert_eq!(format!("{}", Value::Bool(false)), "value bool: false");
+    }
+
+    #[test]
+    fn test_value_display_none() {
+        assert_eq!(format!("{}", Value::None), "None");
+    }
+
+    #[test]
+    fn test_value_display_list() {
+        let list = Value::List(vec![Value::from(1i32), Value::from(2i32)]);
+        assert_eq!(
+            format!("{}", list),
+            "value list: [value number: 1,value number: 2,]"
+        );
+    }
+
+    #[test]
+    fn test_value_display_list_empty() {
+        assert_eq!(format!("{}", Value::List(vec![])), "value list: []");
+    }
+
+    #[test]
+    fn test_value_display_map() {
+        let map = Value::Map(vec![(Value::String("k".into()), Value::from(1i32))]);
+        assert_eq!(
+            format!("{}", map),
+            "value map: {key: value string: k,value: value number: 1; }"
+        );
+    }
+
+    #[test]
+    fn test_value_display_map_empty() {
+        assert_eq!(format!("{}", Value::Map(vec![])), "value map: {}");
+    }
 }