diff --git a/src/error_reporter.rs b/src/error_reporter.rs
index 721c83c..2428d7d 100644
--- a/src/error_reporter.rs
+++ b/src/error_reporter.rs
@@ -1,22 +1,91 @@
-#[derive(Default)]
-pub struct ErrorReporter {
+pub trait ErrorReporter {
+    fn error(&mut self, line: usize, message: &str) {
+        self.report(line, "", message)
+    }
+
+    fn report(&mut self, line: usize, place: &str, message: &str);
+
+    fn reset(&mut self);
+    fn had_error(&self) -> bool;
+}
+
+pub struct ConsoleErrorReporter {
     had_error: bool,
 }
 
-impl ErrorReporter {
-    pub fn error(&mut self, line: usize, message: &str) {
-        self.report(line, "", message)
+impl ConsoleErrorReporter {
+    pub fn new() -> Self {
+        Self { had_error: false }
     }
+}
 
-    pub fn report(&mut self, line: usize, place: &str, message: &str) {
+impl ErrorReporter for ConsoleErrorReporter {
+    fn report(&mut self, line: usize, place: &str, message: &str) {
         eprintln!("[line {}] Error {}: {}", line, place, message);
         self.had_error = true;
     }
 
-    pub fn reset(&mut self) {
+    fn reset(&mut self) {
         self.had_error = false
     }
-    pub fn had_error(&self) -> bool {
+    fn had_error(&self) -> bool {
         self.had_error
     }
 }
+
+#[cfg(test)]
+pub mod testing {
+    use super::ErrorReporter;
+
+    #[derive(Debug, PartialEq, Eq)]
+    pub struct Logline {
+        pub line: usize,
+        pub place: String,
+        pub message: String,
+    }
+
+    impl Logline {
+        pub fn new(line: usize, place: &str, message: &str) -> Self {
+            Self {
+                line,
+                place: place.into(),
+                message: message.into(),
+            }
+        }
+    }
+
+    pub struct VectorErrorReporter {
+        had_error: bool,
+        errors: Vec<Logline>,
+    }
+
+    impl VectorErrorReporter {
+        pub fn new() -> Self {
+            Self {
+                had_error: false,
+                errors: Vec::new(),
+            }
+        }
+        pub fn errors(&self) -> &Vec<Logline> {
+            &self.errors
+        }
+    }
+
+    impl ErrorReporter for VectorErrorReporter {
+        fn report(&mut self, line: usize, place: &str, message: &str) {
+            self.errors.push(Logline {
+                line,
+                place: place.into(),
+                message: message.into(),
+            });
+            self.had_error = true;
+        }
+
+        fn reset(&mut self) {
+            self.had_error = false
+        }
+        fn had_error(&self) -> bool {
+            self.had_error
+        }
+    }
+}
diff --git a/src/expr.rs b/src/expr.rs
index 1772f90..8ae9620 100644
--- a/src/expr.rs
+++ b/src/expr.rs
@@ -31,7 +31,9 @@ impl Expr {
 impl Display for Expr {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            Self::Binary(left, token, right) => write!(f, "({} {} {})", token.token_type, left, right),
+            Self::Binary(left, token, right) => {
+                write!(f, "({} {} {})", token.token_type, left, right)
+            }
             Self::Grouping(expr) => write!(f, "(group {})", expr),
             Self::Literal(literal) => write!(f, "({})", literal),
             Self::Unary(token, right) => write!(f, "({} {})", token.lexeme, right),
diff --git a/src/lox.rs b/src/lox.rs
index f8cdfd8..6324568 100644
--- a/src/lox.rs
+++ b/src/lox.rs
@@ -3,20 +3,29 @@ use std::{
     io::{self, Write},
 };
 
-use crate::{error_reporter::ErrorReporter, parser::Parser, scanner::Scanner};
+use crate::{
+    error_reporter::{ConsoleErrorReporter, ErrorReporter},
+    parser::Parser,
+    scanner::Scanner,
+};
 
-#[derive(Default)]
 pub struct Lox {
-    error_reporter: ErrorReporter,
+    error_reporter: Box<dyn ErrorReporter>,
 }
 
 impl Lox {
+    pub fn new() -> Self {
+        Self {
+            error_reporter: Box::new(ConsoleErrorReporter::new()),
+        }
+    }
+
     fn run(&mut self, source: String) {
-        let mut scanner = Scanner::new(source, &mut self.error_reporter);
+        let mut scanner = Scanner::new(source, self.error_reporter.as_mut());
         let tokens = scanner.scan_tokens();
         // tokens.iter().for_each(|x| println!("{:?}", x));
         if !self.error_reporter.had_error() {
-            let mut parser = Parser::new(tokens);
+            let mut parser = Parser::new(tokens, self.error_reporter.as_mut());
             println!("{}", parser.parse());
         }
     }
diff --git a/src/main.rs b/src/main.rs
index 7ce4ed7..877472c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -13,7 +13,7 @@ mod token;
 
 fn main() {
     let args = Args::parse();
-    let mut lox = Lox::default();
+    let mut lox = Lox::new();
     match args.file {
         Some(file) => {
             if !lox.run_file(file) {
diff --git a/src/parser.rs b/src/parser.rs
index ff37237..6b95a03 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -1,15 +1,21 @@
+use crate::error_reporter::ErrorReporter;
 use crate::expr::Literal::{self, Boolean};
 use crate::{expr::Expr, token::Token};
 
 use crate::token::TokenType::*;
-pub struct Parser {
+pub struct Parser<'a> {
     tokens: Vec<Token>,
     current: usize,
+    error_reporter: &'a mut dyn ErrorReporter,
 }
 
-impl Parser {
-    pub fn new(tokens: Vec<Token>) -> Self {
-        Self { tokens, current: 0 }
+impl<'a> Parser<'a> {
+    pub fn new(tokens: Vec<Token>, error_reporter: &'a mut dyn ErrorReporter) -> Self {
+        Self {
+            tokens,
+            current: 0,
+            error_reporter,
+        }
     }
 
     pub fn parse(&mut self) -> Expr {
@@ -113,7 +119,7 @@ impl Parser {
 mod parser_tests {
 
     use crate::{
-        expr::{Expr, Literal},
+        error_reporter::{testing::VectorErrorReporter, ErrorReporter},
         token::{Token, TokenType},
     };
 
@@ -126,8 +132,10 @@ mod parser_tests {
             token(TokenType::String(string.clone())),
             token(TokenType::Eof),
         ];
-        let mut parser = Parser::new(tokens);
+        let mut error_reporter = VectorErrorReporter::new();
+        let mut parser = Parser::new(tokens, &mut error_reporter);
         let expr = parser.parse();
+        assert!(!error_reporter.had_error());
         assert_eq!(expr.to_string(), r#"("foo")"#);
     }
 
@@ -142,9 +150,14 @@ mod parser_tests {
             token(TokenType::String(string.clone())),
             token(TokenType::Eof),
         ];
-        let mut parser = Parser::new(tokens);
+        let mut error_reporter = VectorErrorReporter::new();
+        let mut parser = Parser::new(tokens, &mut error_reporter);
         let expr = parser.parse();
-        assert_eq!(expr.to_string(), r#"(EqualEqual (BangEqual ("foo") ("foo")) ("foo"))"#);
+        assert!(!error_reporter.had_error());
+        assert_eq!(
+            expr.to_string(),
+            r#"(EqualEqual (BangEqual ("foo") ("foo")) ("foo"))"#
+        );
     }
 
     fn token(token_type: TokenType) -> Token {
diff --git a/src/scanner.rs b/src/scanner.rs
index 31d7d7b..ddac1e8 100644
--- a/src/scanner.rs
+++ b/src/scanner.rs
@@ -11,7 +11,7 @@ pub struct Scanner<'a> {
     start: usize,
     current: usize,
     line: usize,
-    error_reporter: &'a mut ErrorReporter,
+    error_reporter: &'a mut dyn ErrorReporter,
 }
 
 enum ScanResult {
@@ -40,7 +40,7 @@ static KEYWORDS: phf::Map<&'static str, TokenType> = phf_map! {
 };
 
 impl<'a> Scanner<'a> {
-    pub fn new(source: String, e: &'a mut ErrorReporter) -> Self {
+    pub fn new(source: String, e: &'a mut dyn ErrorReporter) -> Self {
         Self {
             source,
             tokens: vec![],
@@ -207,6 +207,9 @@ impl<'a> Scanner<'a> {
 #[cfg(test)]
 mod scanner_tests {
 
+    use crate::error_reporter::testing::Logline;
+    use crate::error_reporter::testing::VectorErrorReporter;
+
     use crate::error_reporter::ErrorReporter;
 
     use super::Scanner;
@@ -215,30 +218,33 @@ mod scanner_tests {
     #[test]
     fn parse_string() {
         let input = "\"test\"";
-        let mut error_reporter = ErrorReporter::default();
+        let mut error_reporter = VectorErrorReporter::new();
         let mut scanner = Scanner::new(input.into(), &mut error_reporter);
         let result = scanner.scan_tokens();
         let head = &result[0].token_type;
+        assert!(!error_reporter.had_error());
         assert_matches!(head, String(x) if x == "test");
     }
     #[test]
     fn parse_float() {
         let input = "1.1";
-        let mut error_reporter = ErrorReporter::default();
+        let mut error_reporter = VectorErrorReporter::new();
         let mut scanner = Scanner::new(input.into(), &mut error_reporter);
         let result = scanner.scan_tokens();
         assert_eq!(result.len(), 2);
         let head = &result[0].token_type;
+        assert!(!error_reporter.had_error());
         assert_matches!(head, Number(_));
     }
     #[test]
     fn parse_identifier() {
         let input = "variable_name";
-        let mut error_reporter = ErrorReporter::default();
+        let mut error_reporter = VectorErrorReporter::new();
         let mut scanner = Scanner::new(input.into(), &mut error_reporter);
         let result = scanner.scan_tokens();
         let head = &result[0];
         let token_type = &head.token_type;
+        assert!(!error_reporter.had_error());
         assert_matches!(token_type, Identifier);
         assert_eq!(head.lexeme, input)
     }
@@ -246,11 +252,28 @@ mod scanner_tests {
     #[test]
     fn parse_for() {
         let input = "for";
-        let mut error_reporter = ErrorReporter::default();
+        let mut error_reporter = VectorErrorReporter::new();
         let mut scanner = Scanner::new(input.into(), &mut error_reporter);
         let result = scanner.scan_tokens();
         let head = &result[0];
         let token_type = &head.token_type;
+        assert!(!error_reporter.had_error());
         assert_matches!(token_type, For);
     }
+
+    #[test]
+    fn raise_error_on_unterminated_string() {
+        let input = "\"";
+        let mut error_reporter = VectorErrorReporter::new();
+        let mut scanner = Scanner::new(input.into(), &mut error_reporter);
+        let result = scanner.scan_tokens();
+        let head = &result[0];
+        let token_type = &head.token_type;
+        assert!(error_reporter.had_error());
+        assert_eq!(
+            error_reporter.errors(),
+            &vec![(Logline::new(1, "", "Unterminated string"))]
+        );
+        assert_matches!(token_type, Eof);
+    }
 }