diff --git a/src/main.rs b/src/main.rs
index f4f7872..9b241ba 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -54,44 +54,6 @@ where
             run_len: 0,
         }
     }
-
-    // A hack to unit test the index lookup behavior. A partial test can be done
-    // to verify the basic indexing principles by preloading a known buffer and
-    // then extracting back-referenced data out of it. A complete test should
-    // feed in other valid operations that populate the backbuffer, and then index
-    // op codes to demonstrate the indexing operations.
-    fn new_with_backbuffer(bytes: I, back_buffer: [PixelRGBA; 64]) -> Self {
-        Self {
-            back_buffer,
-            prev_pixel: PixelRGBA {
-                r: 0,
-                g: 0,
-                b: 0,
-                a: 255,
-            },
-            bytes,
-            run_len: 0,
-        }
-    }
-
-    // A hack to unit test the run behavior. Same idea as the new_with_backbuffer()
-    // function, but for testing a run of pixels.
-    fn new_with_previous_pixel(bytes: I, prev_pixel: PixelRGBA) -> Self {
-        Self {
-            back_buffer: [PixelRGBA::zero(); 64],
-            prev_pixel,
-            bytes,
-            run_len: 0,
-        }
-    }
-
-    pub(crate) fn peek_prev_pixel(&self) -> &PixelRGBA {
-        &self.prev_pixel
-    }
-
-    pub(crate) fn peek_backbuffer(&self, idx: usize) -> &PixelRGBA {
-        &self.back_buffer[idx]
-    }
 }
 
 mod codec_utils {
@@ -198,6 +160,45 @@ where
 #[cfg(test)]
 mod test {
     use super::*;
+    impl <I> Decoder <I> where I: Iterator<Item=u8> {
+        // A hack to unit test the index lookup behavior. A partial test can be done
+        // to verify the basic indexing principles by preloading a known buffer and
+        // then extracting back-referenced data out of it. A complete test should
+        // feed in other valid operations that populate the backbuffer, and then index
+        // op codes to demonstrate the indexing operations.
+        fn new_with_backbuffer(bytes: I, back_buffer: [PixelRGBA; 64]) -> Self {
+            Self {
+                back_buffer,
+                prev_pixel: PixelRGBA {
+                    r: 0,
+                    g: 0,
+                    b: 0,
+                    a: 255,
+                },
+                bytes,
+                run_len: 0,
+            }
+        }
+
+        // A hack to unit test the run behavior. Same idea as the new_with_backbuffer()
+        // function, but for testing a run of pixels.
+        fn new_with_previous_pixel(bytes: I, prev_pixel: PixelRGBA) -> Self {
+            Self {
+                back_buffer: [PixelRGBA::zero(); 64],
+                prev_pixel,
+                bytes,
+                run_len: 0,
+            }
+        }
+
+        fn peek_prev_pixel(&self) -> &PixelRGBA {
+            &self.prev_pixel
+        }
+
+        fn peek_backbuffer(&self, idx: usize) -> &PixelRGBA {
+            &self.back_buffer[idx]
+        }
+    }
 
     #[test] // this is mostly just to drive the function. Make sure it wraps or crashes in debug.
     fn test_backref_hash_function() {