diff --git a/Cargo.toml b/Cargo.toml
index 578fab1..b7b9fd6 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -33,6 +33,8 @@ anyhow = "1.0"
 png = "0.17"
 walkdir = "2.3"
 cfg-if = "1.0"
+rand = "0.8"
+libqoi = { path = "libqoi"}
 
 [lib]
 name = "qoi_fast"
diff --git a/tests/test_gen.rs b/tests/test_gen.rs
new file mode 100644
index 0000000..713a650
--- /dev/null
+++ b/tests/test_gen.rs
@@ -0,0 +1,172 @@
+mod common;
+
+use cfg_if::cfg_if;
+use rand::{rngs::StdRng, Rng, SeedableRng};
+
+use libqoi::{qoi_decode, qoi_encode};
+use qoi_fast::{decode_to_vec, encode_to_vec};
+
+use self::common::hash;
+
+struct GenState<const N: usize> {
+    index: [[u8; N]; 64],
+    pixels: Vec<u8>,
+    prev: [u8; N],
+    len: usize,
+}
+
+impl<const N: usize> GenState<N> {
+    pub fn with_capacity(capacity: usize) -> Self {
+        Self {
+            index: [[0; N]; 64],
+            pixels: Vec::with_capacity(capacity * N),
+            prev: Self::zero(),
+            len: 0,
+        }
+    }
+    pub fn write(&mut self, px: [u8; N]) {
+        self.index[hash(px) as usize] = px;
+        for i in 0..N {
+            self.pixels.push(px[i]);
+        }
+        self.prev = px;
+        self.len += 1;
+    }
+
+    pub fn pick_from_index(&self, rng: &mut impl Rng) -> [u8; N] {
+        self.index[rng.gen_range(0_usize..64)]
+    }
+
+    pub fn zero() -> [u8; N] {
+        let mut px = [0; N];
+        if N >= 4 {
+            px[3] = 0xff;
+        }
+        px
+    }
+}
+
+struct ImageGen {
+    p_new: f64,
+    p_index: f64,
+    p_repeat: f64,
+    p_diff: f64,
+    p_luma: f64,
+}
+
+impl ImageGen {
+    pub fn new_random(rng: &mut impl Rng) -> Self {
+        let p = [0; 6].map(|_| rng.gen::<f64>());
+        let t = p.iter().sum::<f64>();
+        Self {
+            p_new: p[0] / t,
+            p_index: p[1] / t,
+            p_repeat: p[2] / t,
+            p_diff: p[3] / t,
+            p_luma: p[4] / t,
+        }
+    }
+
+    pub fn generate(&self, rng: &mut impl Rng, channels: usize, min_len: usize) -> Vec<u8> {
+        match channels {
+            3 => self.generate_const::<_, 3>(rng, min_len),
+            4 => self.generate_const::<_, 4>(rng, min_len),
+            _ => panic!(),
+        }
+    }
+
+    fn generate_const<R: Rng, const N: usize>(&self, rng: &mut R, min_len: usize) -> Vec<u8> {
+        let mut s = GenState::<N>::with_capacity(min_len);
+        let zero = GenState::<N>::zero();
+
+        while s.len < min_len {
+            let mut p = rng.gen_range(0.0..1.0);
+
+            if p < self.p_new {
+                s.write([0; N].map(|_| rng.gen()));
+                continue;
+            }
+            p -= self.p_new;
+
+            if p < self.p_index {
+                let px = s.pick_from_index(rng);
+                s.write(px);
+                continue;
+            }
+            p -= self.p_index;
+
+            if p < self.p_repeat {
+                let px = s.prev;
+                let n_repeat = rng.gen_range(1_usize..=70);
+                for _ in 0..n_repeat {
+                    s.write(px);
+                }
+                continue;
+            }
+            p -= self.p_repeat;
+
+            if p < self.p_diff {
+                let mut px = s.prev;
+                let d = [0; 3].map(|_| rng.gen_range(0_u8..4).wrapping_sub(2));
+                px[0] = px[0].wrapping_add(d[0]);
+                px[1] = px[1].wrapping_add(d[0]);
+                px[2] = px[2].wrapping_add(d[0]);
+                s.write(px);
+                continue;
+            }
+            p -= self.p_diff;
+
+            if p < self.p_luma {
+                let mut px = s.prev;
+                let vg = rng.gen_range(0_u8..64).wrapping_sub(32);
+                let vr = rng.gen_range(0_u8..16).wrapping_sub(8).wrapping_add(vg);
+                let vb = rng.gen_range(0_u8..16).wrapping_sub(8).wrapping_add(vg);
+                px[0] = px[0].wrapping_add(vr);
+                px[1] = px[1].wrapping_add(vg);
+                px[2] = px[2].wrapping_add(vb);
+                s.write(px);
+                continue;
+            }
+
+            s.write(zero);
+        }
+
+        s.pixels
+    }
+}
+
+#[test]
+fn test_generated() {
+    let mut rng = StdRng::seed_from_u64(0);
+
+    let mut n_pixels = 0;
+    while n_pixels < 20_000_000 {
+        let min_len = rng.gen_range(1..=5000);
+        let channels = rng.gen_range(3..=4);
+        let gen = ImageGen::new_random(&mut rng);
+        let img = gen.generate(&mut rng, channels, min_len);
+        let size = img.len() / channels;
+
+        let encoded = encode_to_vec(&img, size as _, 1).unwrap();
+        let decoded = decode_to_vec(&encoded).unwrap().1;
+        assert_eq!(&img, &decoded, "qoi-fast: roundtrip fail");
+
+        let encoded_c = qoi_encode(&img, size as _, 1, channels as _).unwrap();
+        let decoded_c = qoi_decode(encoded_c.as_ref(), channels as _).unwrap().1;
+        assert_eq!(&img, decoded_c.as_ref(), "qoi.h: roundtrip fail");
+
+        cfg_if! {
+            if #[cfg(feature = "reference")] {
+                assert_eq!(&encoded, encoded_c.as_ref(), "qoi-fast[reference] doesn't match qoi.h");
+            }
+        }
+
+        let encoded_internal_decoded_c = qoi_decode(encoded.as_ref(), channels as _).unwrap().1;
+        assert_eq!(encoded_internal_decoded_c.as_ref(), &img, "qoi-fast -> qoi.h: roundtrip fail");
+
+        let encoded_c_decoded_internal = decode_to_vec(encoded_c.as_ref()).unwrap().1;
+        assert_eq!(&encoded_c_decoded_internal, &img, "qoi.h -> qoi-fast: roundtrip fail");
+
+        n_pixels += size;
+    }
+}