diff --git a/src/corpus/mod.rs b/src/corpus/mod.rs
index e6db9fb483..9a1b18681a 100644
--- a/src/corpus/mod.rs
+++ b/src/corpus/mod.rs
@@ -304,13 +304,10 @@ mod tests {
     #[test]
 
     fn test_queuecorpus() {
-        let rand = Xoshiro256StarRand::new_rc();
+        let rand = Xoshiro256StarRand::new_rr();
         let mut q = QueueCorpus::new(OnDiskCorpus::new(&rand, PathBuf::from("fancy/path")));
         let i = BytesInput::new(vec![0; 4]);
-        let t = Rc::new(RefCell::new(Testcase::new_with_filename(
-            i,
-            PathBuf::from("fancyfile"),
-        )));
+        let t = Testcase::with_filename_rr(i, PathBuf::from("fancyfile"));
         q.add(t);
         let filename = q
             .get()
diff --git a/src/corpus/testcase.rs b/src/corpus/testcase.rs
index 52550e135b..9ba2dce787 100644
--- a/src/corpus/testcase.rs
+++ b/src/corpus/testcase.rs
@@ -2,34 +2,14 @@ use crate::inputs::Input;
 use crate::AflError;
 
 use hashbrown::HashMap;
+use std::cell::RefCell;
 use std::path::PathBuf;
+use std::rc::Rc;
 
 pub trait TestcaseMetadata {
     fn name(&self) -> &'static str;
 }
 
-/*
-pub trait TestcaseTrait<I: Input> {
-    /// Make sure to return a valid input instance loading it from disk if not in memory
-    fn load_input(&mut self) -> Result<&I, AflError>;
-
-    /// Get the input, if any
-    fn input(&self) -> &Option<I>;
-
-    /// Get the input, if any (mutable)
-    fn input_mut(&mut self) -> &mut Option<I>;
-
-    /// Get the filename, if any
-    fn filename(&self) -> &Option<PathBuf>;
-
-    /// Get the filename, if any (mutable)
-    fn filename_mut(&mut self, filename: PathBuf) -> &mut &Option<PathBuf>;
-
-    /// Get all the metadatas into an HashMap
-    fn metadatas(&mut self) -> &mut HashMap<String, Box<dyn TestcaseMetadata>>;
-}
-*/
-
 #[derive(Default)]
 pub struct Testcase<I>
 where
@@ -40,6 +20,8 @@ where
     metadatas: HashMap<&'static str, Box<dyn TestcaseMetadata>>,
 }
 
+pub type TestcaseRef<I> = Rc<RefCell<Testcase<I>>>;
+
 impl<I> Testcase<I>
 where
     I: Input,
@@ -89,7 +71,7 @@ where
         self.metadatas.insert(meta.name(), meta);
     }
 
-    /// Create a new DefaultTestcase instace given an input
+    /// Create a new Testcase instace given an input
     pub fn new(input: I) -> Self {
         Testcase {
             input: Some(input),
@@ -98,12 +80,22 @@ where
         }
     }
 
-    /// Create a new DefaultTestcase instace given an input and a filename
-    pub fn new_with_filename(input: I, filename: PathBuf) -> Self {
+    /// Create a new Testcase instace given an input and a filename
+    pub fn with_filename(input: I, filename: PathBuf) -> Self {
         Testcase {
             input: Some(input),
             filename: Some(filename),
             metadatas: HashMap::default(),
         }
     }
+
+    /// Create a new Testcase instace given an input behind a Rc RefCell
+    pub fn new_rr(input: I) -> Rc<RefCell<Self>> {
+        Rc::new(RefCell::new(Self::new(input)))
+    }
+
+    /// Create a new Testcase instace given an input and a filename behind a Rc RefCell
+    pub fn with_filename_rr(input: I, filename: PathBuf) -> Rc<RefCell<Self>> {
+        Rc::new(RefCell::new(Self::with_filename(input, filename)))
+    }
 }
diff --git a/src/engines/mod.rs b/src/engines/mod.rs
index 19ce6b7fac..85f1e38edf 100644
--- a/src/engines/mod.rs
+++ b/src/engines/mod.rs
@@ -20,7 +20,7 @@ where
     ) -> Result<bool, AflError>;
 }
 
-pub trait Engine<'a, I, C, E>: Evaluator<I>
+pub trait Engine<I, C, E>: Evaluator<I>
 where
     I: Input,
     C: Corpus<I>,
@@ -34,11 +34,11 @@ where
         self.feedbacks_mut().push(feedback);
     }
 
-    fn stages(&self) -> &Vec<Box<dyn Stage<'a, I, E = Self>>>;
+    fn stages(&self) -> &Vec<Box<dyn Stage<I, E = Self>>>;
 
-    fn stages_mut(&mut self) -> &mut Vec<Box<dyn Stage<'a, I, E = Self>>>;
+    fn stages_mut(&mut self) -> &mut Vec<Box<dyn Stage<I, E = Self>>>;
 
-    fn add_stage(&mut self, stage: Box<dyn Stage<'a, I, E = Self>>) {
+    fn add_stage(&mut self, stage: Box<dyn Stage<I, E = Self>>) {
         self.stages_mut().push(stage);
     }
 
@@ -91,19 +91,19 @@ where
     }
 }
 
-pub struct DefaultEngine<'a, I, C, E>
+pub struct DefaultEngine<I, C, E>
 where
     I: Input,
     C: Corpus<I>,
     E: Executor<I>,
 {
     feedbacks: Vec<Box<dyn Feedback<I>>>,
-    stages: Vec<Box<dyn Stage<'a, I, E = Self>>>,
-    executor: &'a mut E,
-    corpus: &'a mut C,
+    stages: Vec<Box<dyn Stage<I, E = Self>>>,
+    executor: E,
+    corpus: C,
 }
 
-impl<'a, I, C, E> Evaluator<I> for DefaultEngine<'a, I, C, E>
+impl<I, C, E> Evaluator<I> for DefaultEngine<I, C, E>
 where
     I: Input,
     C: Corpus<I>,
@@ -118,7 +118,7 @@ where
     }
 }
 
-impl<'a, I, C, E> Engine<'a, I, C, E> for DefaultEngine<'a, I, C, E>
+impl<I, C, E> Engine<I, C, E> for DefaultEngine<I, C, E>
 where
     I: Input,
     C: Corpus<I>,
@@ -132,38 +132,38 @@ where
         &mut self.feedbacks
     }
 
-    fn stages(&self) -> &Vec<Box<dyn Stage<'a, I, E = Self>>> {
+    fn stages(&self) -> &Vec<Box<dyn Stage<I, E = Self>>> {
         &self.stages
     }
 
-    fn stages_mut(&mut self) -> &mut Vec<Box<dyn Stage<'a, I, E = Self>>> {
+    fn stages_mut(&mut self) -> &mut Vec<Box<dyn Stage<I, E = Self>>> {
         &mut self.stages
     }
 
     fn corpus(&self) -> &C {
-        self.corpus
+        &self.corpus
     }
 
     fn corpus_mut(&mut self) -> &mut C {
-        self.corpus
+        &mut self.corpus
     }
 
     fn executor(&self) -> &E {
-        self.executor
+        &self.executor
     }
 
     fn executor_mut(&mut self) -> &mut E {
-        self.executor
+        &mut self.executor
     }
 }
 
-impl<'a, I, C, E> DefaultEngine<'a, I, C, E>
+impl<I, C, E> DefaultEngine<I, C, E>
 where
     I: Input,
     C: Corpus<I>,
     E: Executor<I>,
 {
-    pub fn new(corpus: &'a mut C, executor: &'a mut E) -> Self {
+    pub fn new(corpus: C, executor: E) -> Self {
         DefaultEngine {
             feedbacks: vec![],
             stages: vec![],
@@ -171,11 +171,15 @@ where
             executor: executor,
         }
     }
+
+    pub fn new_rr(corpus: C, executor: E) -> Rc<RefCell<Self>> {
+        Rc::new(RefCell::new(Self::new(corpus, executor)))
+    }
 }
 
 #[cfg(test)]
 mod tests {
-    use crate::corpus::InMemoryCorpus;
+    use crate::corpus::{Corpus, InMemoryCorpus};
     use crate::engines::{DefaultEngine, Engine};
     use crate::executors::inmemory::InMemoryExecutor;
     use crate::executors::{Executor, ExitKind};
@@ -192,14 +196,12 @@ mod tests {
 
     #[test]
     fn test_engine() {
-        let rand = Rc::new(RefCell::new(Xoshiro256StarRand::new()));
+        let rand = Xoshiro256StarRand::new_rr();
         let mut corpus = InMemoryCorpus::<BytesInput, _>::new(&rand);
         let mut executor = InMemoryExecutor::new(harness);
-        let mut engine = DefaultEngine::new(&mut corpus, &mut executor);
-        let stage = Box::new(DefaultMutationalStage::new(&rand, &mut engine));
-        engine.add_stage(stage);
-        engine.fuzz_one().unwrap();
-        let stage1 = Box::new(DefaultMutationalStage::new(&rand, &mut engine));
-        engine.fuzz_one().unwrap();
+        let mut engine = DefaultEngine::new_rr(corpus, executor);
+        let stage = Box::new(DefaultMutationalStage::new(&rand, &engine));
+        engine.borrow_mut().add_stage(stage);
+        engine.borrow_mut().fuzz_one().unwrap();
     }
 }
diff --git a/src/stages/mod.rs b/src/stages/mod.rs
index 4b6a71f0ca..43676df6d2 100644
--- a/src/stages/mod.rs
+++ b/src/stages/mod.rs
@@ -14,12 +14,10 @@ where
 {
     type E: Evaluator<I>;
 
-    fn eval(&self) -> &Self::E;
-
-    fn eval_mut(&mut self) -> &mut Self::E;
+    fn eval(&self) -> &Rc<RefCell<Self::E>>;
 }
 
-pub trait Stage<'a, I>: HasEvaluator<I>
+pub trait Stage<I>: HasEvaluator<I>
 where
     I: Input,
 {
diff --git a/src/stages/mutational.rs b/src/stages/mutational.rs
index 8bd263f525..ac10b014b3 100644
--- a/src/stages/mutational.rs
+++ b/src/stages/mutational.rs
@@ -11,7 +11,7 @@ use std::rc::Rc;
 
 // TODO create HasMutatorsVec trait
 
-pub trait MutationalStage<'a, I>: Stage<'a, I> + HasRand
+pub trait MutationalStage<I>: Stage<I> + HasRand
 where
     I: Input,
 {
@@ -36,7 +36,10 @@ where
                 m.mutate(&mut input, i as i32)?;
             }
 
-            let interesting = self.eval_mut().evaluate_input(&mut input, entry.clone())?;
+            let interesting = self
+                .eval()
+                .borrow_mut()
+                .evaluate_input(&mut input, entry.clone())?;
 
             for m in self.mutators_mut() {
                 m.post_exec(interesting, i as i32)?;
@@ -48,18 +51,18 @@ where
     }
 }
 
-pub struct DefaultMutationalStage<'a, I, R, E>
+pub struct DefaultMutationalStage<I, R, E>
 where
     I: Input,
     R: Rand,
     E: Evaluator<I>,
 {
     rand: Rc<RefCell<R>>,
-    eval: &'a mut E,
+    eval: Rc<RefCell<E>>,
     mutators: Vec<Box<dyn Mutator<I, R = R>>>,
 }
 
-impl<'a, I, R, E> HasRand for DefaultMutationalStage<'a, I, R, E>
+impl<I, R, E> HasRand for DefaultMutationalStage<I, R, E>
 where
     I: Input,
     R: Rand,
@@ -72,7 +75,7 @@ where
     }
 }
 
-impl<'a, I, R, E> HasEvaluator<I> for DefaultMutationalStage<'a, I, R, E>
+impl<I, R, E> HasEvaluator<I> for DefaultMutationalStage<I, R, E>
 where
     I: Input,
     R: Rand,
@@ -80,16 +83,12 @@ where
 {
     type E = E;
 
-    fn eval(&self) -> &Self::E {
-        self.eval
-    }
-
-    fn eval_mut(&mut self) -> &mut Self::E {
-        self.eval
+    fn eval(&self) -> &Rc<RefCell<Self::E>> {
+        &self.eval
     }
 }
 
-impl<'a, I, R, E> MutationalStage<'a, I> for DefaultMutationalStage<'a, I, R, E>
+impl<I, R, E> MutationalStage<I> for DefaultMutationalStage<I, R, E>
 where
     I: Input,
     R: Rand,
@@ -104,7 +103,7 @@ where
     }
 }
 
-impl<'a, I, R, E> Stage<'a, I> for DefaultMutationalStage<'a, I, R, E>
+impl<I, R, E> Stage<I> for DefaultMutationalStage<I, R, E>
 where
     I: Input,
     R: Rand,
@@ -115,16 +114,16 @@ where
     }
 }
 
-impl<'a, I, R, E> DefaultMutationalStage<'a, I, R, E>
+impl<I, R, E> DefaultMutationalStage<I, R, E>
 where
     I: Input,
     R: Rand,
     E: Evaluator<I>,
 {
-    pub fn new(rand: &Rc<RefCell<R>>, eval: &'a mut E) -> Self {
+    pub fn new(rand: &Rc<RefCell<R>>, eval: &Rc<RefCell<E>>) -> Self {
         DefaultMutationalStage {
             rand: Rc::clone(rand),
-            eval: eval,
+            eval: Rc::clone(eval),
             mutators: vec![],
         }
     }
diff --git a/src/utils.rs b/src/utils.rs
index fbfdea27a8..dcfc1891a6 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -41,7 +41,7 @@ pub trait Rand: Debug {
     }
 }
 
-/// Has a Rand box field
+/// Has a Rand Rc RefCell field
 pub trait HasRand {
     type R: Rand;
 
@@ -106,13 +106,13 @@ impl Rand for Xoshiro256StarRand {
 }
 
 impl Xoshiro256StarRand {
-    pub fn new() -> Xoshiro256StarRand {
+    pub fn new() -> Self {
         let mut ret: Xoshiro256StarRand = Default::default();
         ret.set_seed(0); // TODO: Proper random seed?
         ret
     }
 
-    pub fn new_rc() -> Rc<RefCell<Xoshiro256StarRand>> {
+    pub fn new_rr() -> Rc<RefCell<Self>> {
         Rc::new(RefCell::new(Xoshiro256StarRand::new()))
     }
 }
@@ -163,7 +163,7 @@ mod tests {
     }
 
     fn test_has_rand() {
-        let rand = Xoshiro256StarRand::new_rc();
+        let rand = Xoshiro256StarRand::new_rr();
         let has_rand = HasRandTest {
             rand: Rc::clone(&rand),
         };