End-to-end testing of the compile path.

src/backend/runtime.rs

@@ -12,7 +12,7 @@ pub struct RuntimeFunctions {
     _referenced_functions: Vec<String>,
 }
 
-#[derive(Debug, Error)]
+#[derive(Debug, Error, PartialEq)]
 pub enum RuntimeFunctionError {
     #[error("Could not find runtime function named '{0}'")]
     CannotFindRuntimeFunction(String),