diff --git a/src/schema.rs b/src/schema.rs
index 8e10697..dab238d 100644
--- a/src/schema.rs
+++ b/src/schema.rs
@@ -149,7 +149,6 @@ where
   }
 }
 
-/*
 #[cfg(test)]
 mod test {
   use std::cell::RefCell;
@@ -166,11 +165,7 @@ mod test {
     Error(()),
   }
 
-  impl Error for DummySymbolError {
-    fn description(&self) -> &str {
-      return "Description";
-    }
-  }
+  impl Error for DummySymbolError {}
 
   impl fmt::Display for DummySymbolError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -179,28 +174,39 @@ mod test {
   }
 
   #[derive(Debug)]
-  struct DummySymbol<'a> {
-    _execute: &'a dyn Fn() -> Result<(), Box<dyn Error>>,
-    _target_reached: &'a dyn Fn() -> Result<bool, Box<dyn Error>>,
+  struct DummySymbol<T, E> {
+    _target_reached: RefCell<T>,
+    _execute: RefCell<E>,
   }
 
-  impl<'b> Symbol for DummySymbol<'b> {
+  impl<
+      E: Iterator<Item = Result<(), Box<dyn Error>>>,
+      T: Iterator<Item = Result<bool, Box<dyn Error>>>,
+    > Symbol for DummySymbol<T, E>
+  {
     fn target_reached(&self) -> Result<bool, Box<dyn Error>> {
-      (self._target_reached)()
+      self._target_reached.borrow_mut().next().unwrap()
     }
     fn execute(&self) -> Result<(), Box<dyn Error>> {
-      (self._execute)()
+      self._execute.borrow_mut().next().unwrap()
     }
   }
 
-  impl<'a> DummySymbol<'a> {
-    fn new(
-      target_reached: &'a dyn Fn() -> Result<bool, Box<dyn Error>>,
-      execute: &'a dyn Fn() -> Result<(), Box<dyn Error>>,
-    ) -> DummySymbol<'a> {
-      DummySymbol {
-        _target_reached: target_reached,
-        _execute: execute,
+  impl<
+      E: Iterator<Item = Result<(), Box<dyn Error>>>,
+      T: Iterator<Item = Result<bool, Box<dyn Error>>>,
+    > DummySymbol<T, E>
+  {
+    fn new<
+      IE: IntoIterator<IntoIter = E, Item = Result<(), Box<dyn Error>>>,
+      IT: IntoIterator<IntoIter = T, Item = Result<bool, Box<dyn Error>>>,
+    >(
+      target_reached: IT,
+      execute: IE,
+    ) -> Self {
+      Self {
+        _target_reached: RefCell::new(target_reached.into_iter()),
+        _execute: RefCell::new(execute.into_iter()),
       }
     }
   }
@@ -217,44 +223,37 @@ mod test {
 
   impl Logger for DummyLogger {
     fn write(&mut self, line: &str) {
-      self.log.push(From::from(line));
+      self.log.push(line.into());
     }
     fn debug(&mut self, line: &str) {
-      self.log.push(From::from(line));
+      self.log.push(line.into());
     }
   }
 
   #[test]
   fn nothing_needed_to_be_done() {
     let result = InitializingSymbolRunner::new(DummyLogger::new())
-      .run_symbol(&DummySymbol::new(&|| Ok(true), &|| Ok(())));
+      .run_symbol(&DummySymbol::new(vec![Ok(true)], vec![Ok(())]), false);
     assert!(result.is_ok());
   }
 
   #[test]
   fn everything_is_ok() {
-    let first = RefCell::new(true);
-    let result = InitializingSymbolRunner::new(DummyLogger::new()).run_symbol(&DummySymbol::new(
-      &|| {
-        let mut _first = first.borrow_mut();
-        Ok(if *_first {
-          *_first = false;
-          true
-        } else {
-          false
-        })
-      },
-      &|| Ok(()),
-    ));
+    let result = InitializingSymbolRunner::new(DummyLogger::new()).run_symbol(
+      &DummySymbol::new(vec![Ok(true), Ok(false)], vec![Ok(())]),
+      false,
+    );
     assert!(result.is_ok());
   }
 
   #[test]
   fn executing_did_not_change_state() {
-    let result = InitializingSymbolRunner::new(DummyLogger::new())
-      .run_symbol(&DummySymbol::new(&|| Ok(false), &|| Ok(())));
+    let result = InitializingSymbolRunner::new(DummyLogger::new()).run_symbol(
+      &DummySymbol::new(vec![Ok(false), Ok(false)], vec![Ok(())]),
+      false,
+    );
     assert_eq!(
-      result.unwrap_err().description(),
+      result.unwrap_err().to_string(),
       "Target not reached after executing symbol"
     );
   }
@@ -262,11 +261,14 @@ mod test {
   #[test]
   fn executing_did_not_work() {
     let err = InitializingSymbolRunner::new(DummyLogger::new())
-      .run_symbol(&DummySymbol::new(&|| Ok(false), &|| {
-        Err(Box::new(DummySymbolError::Error(())))
-      }))
+      .run_symbol(
+        &DummySymbol::new(
+          vec![Ok(false)],
+          vec![Err(Box::new(DummySymbolError::Error(())) as Box<dyn Error>)],
+        ),
+        false,
+      )
       .unwrap_err();
-    assert_eq!(err.description(), "Description");
+    assert_eq!(err.to_string(), "Dummy symbol error");
   }
 }
-*/