test mutable circuit variables

compiler/tests/mutability/circuit_function_mut.leo

@@ -0,0 +1,9 @@
+// Adding the `mut` keyword makes a circuit variable mutable.
+circuit Foo {
+    function bar() {}
+}
+
+function main() {
+    let mut a = Foo { x: 1 };
+    a.bar = 0;
+}

compiler/tests/mutability/circuit_static_function_mut.leo

@@ -0,0 +1,9 @@
+// Adding the `mut` keyword makes a circuit variable mutable.
+circuit Foo {
+    static function bar() {}
+}
+
+function main() {
+    let mut a = Foo { x: 1 };
+    a.bar = 0;
+}

compiler/tests/mutability/circuit_variable_mut.leo

@@ -0,0 +1,11 @@
+// Adding the `mut` keyword makes a circuit variable mutable.
+circuit Foo {
+    mut x: u32
+}
+
+function main() {
+    let mut a = Foo { x: 1 };
+    a.x = 0;
+
+    console.assert(a.x == 0u32);
+}

compiler/tests/mutability/mod.rs

@@ -78,9 +78,33 @@ fn test_circuit_mut() {
     let bytes = include_bytes!("circuit_mut.leo");
     let program = parse_program(bytes).unwrap();
 
+    expect_compiler_error(program);
+}
+
+#[test]
+fn test_circuit_variable_mut() {
+    let bytes = include_bytes!("circuit_variable_mut.leo");
+    let program = parse_program(bytes).unwrap();
+
     assert_satisfied(program);
 }
 
+#[test]
+fn test_circuit_function_mut() {
+    let bytes = include_bytes!("circuit_function_mut.leo");
+    let program = parse_program(bytes).unwrap();
+
+    expect_compiler_error(program);
+}
+
+#[test]
+fn test_circuit_static_function_mut() {
+    let bytes = include_bytes!("circuit_static_function_mut.leo");
+    let program = parse_program(bytes).unwrap();
+
+    expect_compiler_error(program);
+}
+
 #[test]
 fn test_function_input() {
     let bytes = include_bytes!("function_input.leo");