From 003c346439ae59b76111e28be810fadf76d72769 Mon Sep 17 00:00:00 2001
From: Dominik Maier <domenukk@gmail.com>
Date: Fri, 13 Nov 2020 02:55:08 +0100
Subject: [PATCH] reproducible rand for testcases

---
 src/mutators/scheduled.rs |  5 +++--
 src/utils.rs              | 29 +++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/src/mutators/scheduled.rs b/src/mutators/scheduled.rs
index f98be1fb66..e211dd578f 100644
--- a/src/mutators/scheduled.rs
+++ b/src/mutators/scheduled.rs
@@ -327,12 +327,12 @@ mod tests {
     use crate::corpus::{Corpus, InMemoryCorpus};
     use crate::inputs::{BytesInput, HasBytesVec};
     use crate::mutators::scheduled::mutation_splice;
-    use crate::utils::{DefaultHasRand, DefaultRand};
+    use crate::utils::{DefaultHasRand, Rand, XKCDRand};
 
     #[test]
     fn test_mut_splice() {
         // With the current impl, seed of 1 will result in a split at pos 2.
-        let rand = &DefaultRand::new_rr(1);
+        let rand = &XKCDRand::new_rr();
         let mut has_rand = DefaultHasRand::new(&rand);
         let mut corpus = InMemoryCorpus::new(&rand);
         corpus.add_input(BytesInput::new(vec!['a' as u8, 'b' as u8, 'c' as u8]));
@@ -342,6 +342,7 @@ mod tests {
         let mut testcase = testcase_rr.borrow_mut();
         let mut input = testcase.load_input().expect("No input in testcase").clone();
 
+        rand.borrow_mut().set_seed(5);
         mutation_splice(&mut has_rand, &mut corpus, &mut input).unwrap();
 
         println!("{:?}", input.bytes());
diff --git a/src/utils.rs b/src/utils.rs
index 51bed50a56..0b6d3eac91 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -137,6 +137,35 @@ impl Xoshiro256StarRand {
     }
 }
 
+#[cfg(test)]
+/// fake rand, for testing purposes
+#[derive(Copy, Clone, Debug, Default)]
+pub struct XKCDRand {
+    val: u64,
+}
+
+#[cfg(test)]
+impl Rand for XKCDRand {
+    fn set_seed(&mut self, val: u64) {
+        self.val = val
+    }
+
+    fn next(&mut self) -> u64 {
+        self.val
+    }
+}
+
+#[cfg(test)]
+impl XKCDRand {
+    pub fn new() -> Self {
+        Self { val: 4 }
+    }
+
+    pub fn new_rr() -> Rc<RefCell<Self>> {
+        Rc::new(RefCell::new(Self::new()))
+    }
+}
+
 /// A very basic HasRand
 pub struct DefaultHasRand<R>
 where