diff --git a/Cargo.lock b/Cargo.lock
index 6722a0f..820fca2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -244,6 +244,14 @@ dependencies = [
 name = "dvm-lib"
 version = "0.1.0"
 
+[[package]]
+name = "e2e-tests"
+version = "0.1.0"
+dependencies = [
+ "dmc-lib",
+ "dvm-lib",
+]
+
 [[package]]
 name = "encoding_rs"
 version = "0.8.35"
diff --git a/Cargo.toml b/Cargo.toml
index 4a95eea..0a8f58b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -25,4 +25,4 @@ cst-test-generator = { path = "cst-test-generator" }
 
 [workspace]
 resolver = "3"
-members = ["ast-generator", "cst-test-generator", "dm", "dm-std-lib", "dmc-lib", "dvm-lib"]
+members = ["ast-generator", "cst-test-generator", "dm", "dm-std-lib", "dmc-lib", "dvm-lib", "e2e-tests"]
diff --git a/dm/src/main.rs b/dm/src/main.rs
index ec87e68..2bcb942 100644
--- a/dm/src/main.rs
+++ b/dm/src/main.rs
@@ -105,7 +105,7 @@ fn main() {
         &mut registers,
         &mut call_stack,
         "main",
-        vec![],
+        &vec![],
     );
     if let Some(value) = result {
         println!("{}", value);
diff --git a/dvm-lib/src/vm/mod.rs b/dvm-lib/src/vm/mod.rs
index 0677686..0091539 100644
--- a/dvm-lib/src/vm/mod.rs
+++ b/dvm-lib/src/vm/mod.rs
@@ -218,7 +218,7 @@ pub fn call<'a>(
     registers: &mut Vec<Value>,
     call_stack: &mut CallStack<'a>,
     function_name: &str,
-    arguments: Vec<Value>,
+    arguments: &[Value],
 ) -> Option<Value> {
     // check if DVM_DEBUG is enabled
     let debug = std::env::var("DVM_DEBUG")
@@ -234,10 +234,13 @@ pub fn call<'a>(
     call_stack.push(CallFrame::new(function));
 
     // put each arg on the stack
-    for argument in &arguments {
+    for argument in arguments {
         call_stack.top_mut().stack_mut().push(argument.clone());
     }
 
+    // set fp for this function
+    call_stack.top_mut().set_fp(arguments.len());
+
     // ensure enough stack space
     call_stack.top_mut().stack_mut().resize(
         arguments.len() + (function.stack_size() as usize),
@@ -314,6 +317,12 @@ pub fn call<'a>(
                 let mut args =
                     call_stack.top().stack()[call_stack.top().stack().len() - arg_count..].to_vec();
 
+                // save registers
+                for register in registers.iter_mut() {
+                    let value = std::mem::take(register);
+                    call_stack.top_mut().stack_mut().push(value);
+                }
+
                 // increment caller frame ip
                 call_stack.top_mut().increment_ip();
 
@@ -482,9 +491,17 @@ pub fn call<'a>(
                 let mut callee = call_stack.pop(); // pop this frame
                 let maybe_caller = call_stack.maybe_top_mut();
                 if let Some(caller) = maybe_caller {
+                    // restore registers
+                    for i in (0..registers.len()).rev() {
+                        registers[i] = caller.stack_mut().pop().unwrap();
+                    }
+
+                    // pop args
                     for _ in 0..callee.function().parameter_count() {
                         caller.stack_mut().pop();
                     }
+
+                    // push return value if some
                     if let Some(return_value) = callee.take_return_value() {
                         // n.b. callee
                         caller.stack_mut().push(return_value);
diff --git a/dvm-lib/src/vm/value.rs b/dvm-lib/src/vm/value.rs
index 8d8c83c..60f0281 100644
--- a/dvm-lib/src/vm/value.rs
+++ b/dvm-lib/src/vm/value.rs
@@ -1,7 +1,7 @@
 use std::fmt::{Display, Formatter};
 use std::rc::Rc;
 
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, PartialEq, Eq)]
 pub enum Value {
     Int(i32),
     String(Rc<str>),
diff --git a/e2e-tests/Cargo.toml b/e2e-tests/Cargo.toml
new file mode 100644
index 0000000..679fef5
--- /dev/null
+++ b/e2e-tests/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "e2e-tests"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+dmc-lib = { path = "../dmc-lib" }
+dvm-lib = { path = "../dvm-lib" }
\ No newline at end of file
diff --git a/e2e-tests/src/lib.rs b/e2e-tests/src/lib.rs
new file mode 100644
index 0000000..de304db
--- /dev/null
+++ b/e2e-tests/src/lib.rs
@@ -0,0 +1,128 @@
+#[cfg(test)]
+mod e2e_tests {
+    use dmc_lib::constants_table::ConstantsTable;
+    use dmc_lib::diagnostic::Diagnostic;
+    use dmc_lib::parser::parse_compilation_unit;
+    use dmc_lib::symbol_table::SymbolTable;
+    use dvm_lib::vm::constant::{Constant, StringConstant};
+    use dvm_lib::vm::function::Function;
+    use dvm_lib::vm::value::Value;
+    use dvm_lib::vm::{CallStack, DvmContext, call};
+    use std::rc::Rc;
+
+    const REGISTER_COUNT: usize = 8;
+
+    fn report_diagnostics(diagnostics: &[Diagnostic]) -> ! {
+        eprintln!(
+            "{}",
+            diagnostics
+                .iter()
+                .map(|d| format!("{:?}", d))
+                .collect::<Vec<_>>()
+                .join("\n")
+        );
+        panic!("There were diagnostics.");
+    }
+
+    fn assert_result(input: &str, function_name: &str, arguments: &[Value], expected_value: Value) {
+        let parse_result = parse_compilation_unit(input);
+        let mut compilation_unit = match parse_result {
+            Ok(compilation_unit) => compilation_unit,
+            Err(diagnostics) => {
+                report_diagnostics(&diagnostics);
+            }
+        };
+
+        let mut symbol_table = SymbolTable::new();
+
+        let gather_names_diagnostics = compilation_unit.gather_declared_names(&mut symbol_table);
+        if !gather_names_diagnostics.is_empty() {
+            report_diagnostics(&gather_names_diagnostics);
+        }
+
+        let name_usages_diagnostics = compilation_unit.check_name_usages(&symbol_table);
+        if !name_usages_diagnostics.is_empty() {
+            report_diagnostics(&name_usages_diagnostics);
+        }
+
+        let type_check_diagnostics = compilation_unit.type_check(&symbol_table);
+        if !type_check_diagnostics.is_empty() {
+            report_diagnostics(&type_check_diagnostics);
+        }
+
+        let mut ir_functions = compilation_unit.to_ir(&symbol_table);
+
+        let mut functions: Vec<Function> = vec![];
+        let mut constants_table = ConstantsTable::new();
+
+        for ir_function in &mut ir_functions {
+            let (_, stack_size) = ir_function.assign_registers(REGISTER_COUNT);
+            let function = ir_function.assemble(stack_size, &mut constants_table);
+            functions.push(function);
+        }
+
+        let mut dvm_context = DvmContext::new();
+
+        for function in functions {
+            dvm_context
+                .functions_mut()
+                .insert(function.name_owned(), function);
+        }
+
+        for (name, content) in &constants_table.string_constants() {
+            dvm_context.constants_mut().insert(
+                name.clone(),
+                Constant::String(StringConstant::new(name.clone(), content.clone())),
+            );
+        }
+
+        let mut registers: Vec<Value> = vec![Value::Null; REGISTER_COUNT];
+        let mut call_stack = CallStack::new();
+
+        let result = call(
+            &dvm_context,
+            &mut registers,
+            &mut call_stack,
+            function_name,
+            &arguments,
+        );
+        match result {
+            None => panic!("Call returned no value"),
+            Some(result_value) => {
+                assert_eq!(result_value, expected_value);
+            }
+        }
+    }
+
+    #[test]
+    fn add_1_2() {
+        assert_result(
+            "
+            fn add(a: Int, b: Int) -> Int
+                a + b
+            end
+            ",
+            "add",
+            &vec![Value::Int(1), Value::Int(2)],
+            Value::Int(3),
+        );
+    }
+
+    #[test]
+    fn bunch_of_adding() {
+        assert_result(
+            "
+            fn add(a: Int, b: Int) -> Int
+                a + b
+            end
+
+            fn greetAndAdd(a: Int, b: Int) -> String
+                \"Hello. \" + a + \" plus \" + b + \" is \" + add(a, b)
+            end
+            ",
+            "greetAndAdd",
+            &vec![Value::Int(1), Value::Int(2)],
+            Value::String(Rc::from("Hello. 1 plus 2 is 3")),
+        );
+    }
+}
diff --git a/examples/add_2.dm b/examples/add_2.dm
new file mode 100644
index 0000000..2dc8b4b
--- /dev/null
+++ b/examples/add_2.dm
@@ -0,0 +1,13 @@
+extern fn println(message: Any) -> Void
+
+fn add(a: Int, b: Int) -> Int
+    a + b
+end
+
+fn main() -> String
+    let a = 9
+    let b = 7
+    let c = add(a, b)
+    let msg = "Hello. " + a + " plus " + b + " is " + c
+    msg
+end