diff --git a/src/interpreter/interpreter.rs b/src/interpreter/interpreter.rs
index e4c111d..d2a8c4e 100644
--- a/src/interpreter/interpreter.rs
+++ b/src/interpreter/interpreter.rs
@@ -274,30 +274,46 @@ pub fn evaluate_expression(env: &mut Env, expr: Box<Expression>) -> BoxFuture<'_
             Expression::PreIncrement(_, expr) => {
                 let current_value = evaluate_expression(env, expr.clone()).await?;
                 let lhs = Lhs::try_from_expr(expr.as_ref().clone(), env).await?;
-                let new_value = (current_value + 1.into())?;
+                let new_value = (current_value + 1u64.into())?;
                 lhs.execute_assign(new_value.clone(), env)?;
                 Ok(new_value)
             }
             Expression::PreDecrement(_, expr) => {
                 let current_value = evaluate_expression(env, expr.clone()).await?;
                 let lhs = Lhs::try_from_expr(expr.as_ref().clone(), env).await?;
-                let new_value = (current_value - 1.into())?;
+                let new_value = (current_value - 1u64.into())?;
                 lhs.execute_assign(new_value.clone(), env)?;
                 Ok(new_value)
             }
             Expression::PostIncrement(_, expr) => {
                 let current_value = evaluate_expression(env, expr.clone()).await?;
                 let lhs = Lhs::try_from_expr(expr.as_ref().clone(), env).await?;
-                lhs.execute_assign((current_value.clone() + 1.into())?, env)?;
+                lhs.execute_assign((current_value.clone() + 1u64.into())?, env)?;
                 Ok(current_value)
             }
             Expression::PostDecrement(_, expr) => {
                 let current_value = evaluate_expression(env, expr.clone()).await?;
                 let lhs = Lhs::try_from_expr(expr.as_ref().clone(), env).await?;
-                lhs.execute_assign((current_value.clone() - 1.into())?, env)?;
+                lhs.execute_assign((current_value.clone() - 1u64.into())?, env)?;
                 Ok(current_value)
             }
 
+            Expression::AssignAdd(_, left, right) => {
+                _eval_binop_assign(env, left, right, |a, b| a + b).await
+            }
+            Expression::AssignSubtract(_, left, right) => {
+                _eval_binop_assign(env, left, right, |a, b| a - b).await
+            }
+            Expression::AssignMultiply(_, left, right) => {
+                _eval_binop_assign(env, left, right, |a, b| a * b).await
+            }
+            Expression::AssignDivide(_, left, right) => {
+                _eval_binop_assign(env, left, right, |a, b| a / b).await
+            }
+            Expression::AssignModulo(_, left, right) => {
+                _eval_binop_assign(env, left, right, |a, b| a % b).await
+            }
+
             Expression::HexNumberLiteral(_, n, _) => {
                 let result = if n.len() == 42 {
                     Value::Addr(Address::from_hex(n)?)
@@ -610,3 +626,18 @@ where
     let rhs = evaluate_expression(env, rexpr).await?;
     f(lhs, rhs)
 }
+
+async fn _eval_binop_assign<F>(
+    env: &mut Env,
+    lexpr: Box<Expression>,
+    rexpr: Box<Expression>,
+    f: F,
+) -> Result<Value>
+where
+    F: FnOnce(Value, Value) -> Result<Value>,
+{
+    let lhs = Lhs::try_from_expr(lexpr.as_ref().clone(), env).await?;
+    let new_value = _eval_binop(env, lexpr, rexpr, f).await?;
+    lhs.execute_assign(new_value.clone(), env)?;
+    Ok(new_value)
+}
diff --git a/src/interpreter/value.rs b/src/interpreter/value.rs
index 86f5a7a..425115d 100644
--- a/src/interpreter/value.rs
+++ b/src/interpreter/value.rs
@@ -202,6 +202,12 @@ impl From<u128> for Value {
     }
 }
 
+impl From<&str> for Value {
+    fn from(s: &str) -> Self {
+        Value::Str(s.to_string())
+    }
+}
+
 impl<const N: usize> From<alloy::primitives::FixedBytes<N>> for Value {
     fn from(bytes: alloy::primitives::FixedBytes<N>) -> Self {
         Value::FixBytes(B256::from_slice(&bytes[..]), N)
@@ -268,6 +274,7 @@ impl Value {
         }
     }
 
+    #[allow(clippy::len_without_is_empty)]
     pub fn len(&self) -> Result<usize> {
         let len = match self {
             Value::Array(items) => items.len(),
diff --git a/tests/interpreter_test.rs b/tests/interpreter_test.rs
new file mode 100644
index 0000000..1fbb2d4
--- /dev/null
+++ b/tests/interpreter_test.rs
@@ -0,0 +1,121 @@
+use eclair::interpreter::{self, Config, Env, Type, Value};
+
+#[tokio::test]
+async fn test_binops() {
+    let mut env = _create_env();
+
+    _check_result(&mut env, "1 + 8", Value::from(9u64)).await;
+    _check_result(&mut env, "int256(1) - 8", Value::from(-7)).await;
+    _check_result(&mut env, "3 + 8 * 4", Value::from(35u64)).await;
+    _check_result(&mut env, "(10 + 4) % 3", Value::from(2u64)).await;
+}
+
+#[tokio::test]
+async fn test_string() {
+    let mut env = _create_env();
+
+    _check_result(&mut env, "\"foo\"", Value::from("foo")).await;
+    _check_result(&mut env, "\"foo\".length", Value::from(3u64)).await;
+    _check_result(&mut env, "\"foo\".concat(\"bar\")", Value::from("foobar")).await;
+}
+
+#[tokio::test]
+async fn test_builtin_type() {
+    let mut env = _create_env();
+
+    _check_result(&mut env, "type(1)", Value::TypeObject(Type::Uint(256))).await;
+    _check_result(
+        &mut env,
+        "type(uint256)",
+        Value::TypeObject(Type::Type(Box::new(Type::Uint(256)))),
+    )
+    .await;
+}
+
+#[tokio::test]
+async fn test_builtin_format() {
+    let mut env = _create_env();
+
+    _check_result(&mut env, "2e18.format()", Value::from("2.00")).await;
+    _check_result(&mut env, "3.5678e7.format(6)", Value::from("35.68")).await;
+    _check_result(&mut env, "\"foo\".format()", Value::from("foo")).await;
+}
+
+#[tokio::test]
+async fn test_defined_functions() {
+    let mut env = _create_env();
+
+    _execute(&mut env, "function add(a, b) { return a + b; }").await;
+    _check_result(&mut env, "add(1, 2)", Value::from(3u64)).await;
+
+    _execute(
+        &mut env,
+        "function cond(pred, yes, no) { if (pred) return yes; else return no; }",
+    )
+    .await;
+    _check_result(&mut env, "cond(true, 1, 2)", Value::from(1u64)).await;
+    _check_result(&mut env, "cond(false, 1, 2)", Value::from(2u64)).await;
+}
+
+#[tokio::test]
+async fn test_for_loop() {
+    let mut env = _create_env();
+
+    let res = _execute(
+        &mut env,
+        r#"
+        a = 1;
+        for (i = 1; i <= 5; i++) {
+            a *= i;
+        }
+        a;
+    "#,
+    )
+    .await;
+    assert_eq!(res, Some(Value::from(120u64)));
+
+    let res = _execute(
+        &mut env,
+        r#"
+        a = 1;
+        for (i = 1; i <= 5; i++) {
+            if (a > 10) break;
+            a *= i;
+        }
+        a
+    "#,
+    )
+    .await;
+    assert_eq!(res, Some(Value::from(24u64)));
+
+    let res = _execute(
+        &mut env,
+        r#"
+        a = 1;
+        for (i = 1; i <= 5; i++) {
+            if (i % 2 == 0) continue;
+            a *= i;
+        }
+        a
+    "#,
+    )
+    .await;
+    assert_eq!(res, Some(Value::from(15u64)));
+}
+
+async fn _execute(env: &mut Env, code: &str) -> Option<Value> {
+    interpreter::evaluate_code(env, code).await.unwrap()
+}
+
+async fn _check_result(env: &mut Env, code: &str, expected: Value) {
+    let res = _execute(env, code).await;
+    assert_eq!(res, Some(expected));
+}
+
+fn _create_env() -> Env {
+    let foundry_conf = foundry_config::load_config();
+    let config = Config::new(None, false, foundry_conf);
+    let mut env = Env::new(config);
+    interpreter::load_builtins(&mut env);
+    env
+}