diff --git a/Cargo.lock b/Cargo.lock
index c1f12953..2846e5a4 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2020,6 +2020,7 @@ dependencies = [
  "iceberg-catalog-memory",
  "once_cell",
  "ordered-float 5.0.0",
+ "rand 0.8.5",
  "tempfile",
  "tokio",
  "trait-variant",
diff --git a/optd/Cargo.toml b/optd/Cargo.toml
index 275a5ef4..b06faf6c 100644
--- a/optd/Cargo.toml
+++ b/optd/Cargo.toml
@@ -28,3 +28,4 @@ tokio = { version = "1.45.0", features = [
     "rt-multi-thread",
     "test-util"
 ] }
+rand = "0.8.5"
diff --git a/optd/src/memo/fuzz.rs b/optd/src/memo/fuzz.rs
new file mode 100644
index 00000000..4454959e
--- /dev/null
+++ b/optd/src/memo/fuzz.rs
@@ -0,0 +1,259 @@
+use crate::cir::{Child, GroupId, LogicalExpression, LogicalProperties, OperatorData};
+use crate::memo::Memo;
+use rand::distributions::WeightedIndex;
+use rand::prelude::*;
+use rand::rngs::StdRng;
+use std::cmp::max;
+use std::collections::HashSet;
+
+#[derive(Clone, Debug)]
+pub(crate) struct FuzzExpression {
+    pub op: usize,
+    pub children: Vec<usize>,
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct FuzzGroup {
+    pub exprs: Vec<usize>,
+    pub id: usize,
+}
+
+#[derive(Clone, Debug)]
+pub(crate) struct FuzzData {
+    pub exprs: Vec<FuzzExpression>,
+    pub groups: Vec<FuzzGroup>,
+    pub entry: usize,
+}
+
+impl FuzzData {
+    pub fn new(ngroups: usize, nexprs: usize, dag: bool, seed: u64) -> Self {
+        let mut rng = StdRng::seed_from_u64(seed);
+
+        // FIXME: MAGIC NUMBERS
+        let weights = [10, 30, 30]; // distribution operator arity
+        let proximity = 4; // proximity factor (1 for no proximity preference)
+
+        let mut memo = FuzzData {
+            exprs: Vec::new(),
+            groups: Vec::new(),
+            entry: 0,
+        };
+
+        let mut tot = 0;
+        let mut cnt = 0;
+        for (i, v) in weights.iter().enumerate() {
+            tot += i * v;
+            cnt += v;
+        }
+        let dist = WeightedIndex::new(&weights).unwrap();
+
+        // Generate groups
+        let mut gqueue: Vec<usize> = vec![];
+        while memo.groups.len() < ngroups || gqueue.len() > 1 {
+            let mut exprs: Vec<usize> = vec![];
+
+            let ngen = rng.gen_range(0..nexprs * 2);
+
+            // Generate expressions even if no groups to reference (will be a scan!)
+            while exprs.len() < ngen {
+                let arity = dist.sample(&mut rng);
+                let mut children: Vec<usize> = vec![];
+                let mut cset: HashSet<usize> = HashSet::new();
+                for i in 0..arity {
+                    if gqueue.len() > 0 {
+                        let idx = rng.gen_range(0..gqueue.len());
+                        // avoid using the same group twice
+                        // as an operand to the same expression
+                        let c = gqueue[idx];
+                        if !cset.contains(&c) {
+                            cset.insert(c);
+                            children.push(gqueue[idx]);
+                            gqueue.remove(idx);
+                        }
+                    }
+                    if children.len() <= i {
+                        // failed to find a group, make one extra 'scan' node now
+                        children.push(memo.groups.len());
+                        memo.groups.push(FuzzGroup {
+                            exprs: vec![memo.exprs.len()],
+                            id: memo.groups.len(),
+                        });
+                        memo.exprs.push(FuzzExpression {
+                            op: 0,
+                            children: vec![],
+                        });
+                    }
+                }
+                let expr_id = memo.exprs.len();
+                exprs.push(expr_id);
+
+                let op = children.len(); // FIXME: more ops?
+                memo.exprs.push(FuzzExpression { op, children });
+            }
+
+            if ngen > 0 {
+                let group_id = memo.groups.len();
+                memo.groups.push(FuzzGroup {
+                    exprs,
+                    id: group_id,
+                });
+
+                // While we don't have enough groups, collect operands for future expressions
+                if group_id < ngroups && dag {
+                    // replenish groups to be referenced
+                    let ng = match nexprs * tot / cnt {
+                        d if d > 0 => rng.gen_range(0..d * 2),
+                        _ => 0,
+                    };
+
+                    let m = max(0, (group_id as i32) - (ngroups as i32) / proximity) as usize;
+                    for _ in 0..ng {
+                        gqueue.push(rng.gen_range(m..group_id + 1));
+                    }
+                }
+
+                // Add at least this group, so that it is referenced or the last
+                gqueue.push(group_id);
+            }
+        }
+
+        memo.entry = gqueue[0];
+
+        memo
+    }
+
+    pub fn shuffle(&self, chunk: usize, merge: bool) -> FuzzData {
+        assert!(chunk > 1);
+
+        let mut groups = self.groups.clone();
+        let mut i = 0;
+
+        while i < groups.len() {
+            let g = &groups[i];
+            let gid = g.id;
+            if g.exprs.len() > chunk {
+                let upd = g.exprs[..chunk].to_vec();
+                let rest = if merge {
+                    // trigger merge 1,2,3,4,5,6,7 --> 1,2,3 + 4,5,6 + 7,1,4
+                    let mut v = g.exprs[chunk..].to_vec();
+                    v.push(g.exprs[0]);
+                    v
+                } else {
+                    // don't trigger merge 1,2,3,4,5,6,7 --> 1,2,3 - 3,4,5, - 5,6,7
+                    g.exprs[chunk - 1..].to_vec()
+                };
+                groups[i].exprs = upd;
+                groups.push(FuzzGroup {
+                    exprs: rest,
+                    id: gid,
+                })
+            }
+            i = i + 1;
+        }
+
+        FuzzData {
+            exprs: self.exprs.clone(),
+            groups,
+            entry: self.entry,
+        }
+    }
+}
+
+pub struct Fuzzer<M: Memo> {
+    memo: M,
+    group_ids: Vec<GroupId>,
+    entry: GroupId,
+}
+
+impl<M: Memo> Fuzzer<M> {
+    pub fn new(memo: M) -> Self {
+        Self {
+            memo,
+            group_ids: Vec::new(),
+            entry: GroupId(0),
+        }
+    }
+
+    pub async fn add(&mut self, memo: &FuzzData) {
+        for g in memo.groups.iter() {
+            let mut group_id = None;
+
+            for j in g.exprs.iter() {
+                let e = &memo.exprs[*j];
+
+                let expr = match e.op {
+                    0 => LogicalExpression {
+                        tag: "Scan".to_string(),
+                        data: vec![OperatorData::Int64(*j as i64)],
+                        children: vec![],
+                    },
+                    1 => LogicalExpression {
+                        tag: "Filter".to_string(),
+                        data: vec![OperatorData::Int64(*j as i64)],
+                        children: vec![Child::Singleton(self.group_ids[e.children[0]])],
+                    },
+                    2 => LogicalExpression {
+                        tag: "Filter".to_string(),
+                        data: vec![OperatorData::Int64(*j as i64)],
+                        children: vec![
+                            Child::Singleton(self.group_ids[e.children[0]]),
+                            Child::Singleton(self.group_ids[e.children[1]]),
+                        ],
+                    },
+                    _ => unreachable!(),
+                };
+
+                let eid = self.memo.get_logical_expr_id(&expr).await.unwrap();
+                let gid = match self.memo.find_logical_expr_group(eid).await.unwrap() {
+                    None => {
+                        // new expression, create a (temporary) group
+                        self.memo
+                            .create_group(eid, &LogicalProperties(None))
+                            .await
+                            .unwrap()
+                    }
+                    Some(id) => {
+                        // expression already existed, just use its group
+                        id
+                    }
+                };
+
+                if let Some(id) = group_id {
+                    // merge with known equivalent expressions
+                    self.memo.merge_groups(gid, id).await.unwrap();
+                }
+                group_id = Some(gid);
+            }
+            if g.id >= self.group_ids.len() {
+                self.group_ids.push(group_id.unwrap());
+            } else {
+                self.group_ids[g.id] = group_id.unwrap();
+            }
+        }
+
+        self.entry = self.group_ids[memo.entry];
+    }
+
+    pub async fn check(&mut self, memo: &FuzzData) {
+        let mut _tot = 0;
+        for g in 0..memo.groups.len() {
+            let group_expressions = self
+                .memo
+                .get_all_logical_exprs(self.group_ids[g])
+                .await
+                .unwrap();
+
+            // do something with it
+            let mut ids = vec![];
+            for eid in group_expressions {
+                let expr = self.memo.materialize_logical_expr(eid).await.unwrap();
+                if let OperatorData::Int64(v) = expr.data[0] {
+                    ids.push(v as usize);
+                }
+            }
+
+            ids.sort();
+            assert_eq!(ids, memo.groups[g].exprs, "incorrect memo")
+        }
+    }
+}
diff --git a/optd/src/memo/memory/implementation.rs b/optd/src/memo/memory/implementation.rs
index 3f79f2ac..9420bec4 100644
--- a/optd/src/memo/memory/implementation.rs
+++ b/optd/src/memo/memory/implementation.rs
@@ -302,10 +302,9 @@ impl Memo for MemoryMemo {
 #[cfg(test)]
 pub mod tests {
     use super::*;
-    use crate::{
-        cir::{Child, OperatorData},
-        memo::Materialize,
-    };
+    use crate::cir::{Child, OperatorData};
+    use crate::memo::Materialize;
+    use crate::memo::fuzz::{FuzzData, Fuzzer};
 
     pub async fn lookup_or_insert(
         memo: &mut impl Memo,
@@ -697,6 +696,17 @@ pub mod tests {
         );
     }
 
+    #[tokio::test]
+    async fn test_logical_fuzzing() {
+        let data = FuzzData::new(100, 10, true, 12345);
+        let shuffled = data.shuffle(2, true);
+
+        let memo = MemoryMemo::default();
+        let mut fuzzer = Fuzzer::new(memo);
+        fuzzer.add(&shuffled).await;
+        fuzzer.check(&data).await;
+    }
+
     #[tokio::test]
     async fn test_goal_merge() {
         let mut memo = MemoryMemo::default();
diff --git a/optd/src/memo/mod.rs b/optd/src/memo/mod.rs
index fe7ba5ea..9a5fc752 100644
--- a/optd/src/memo/mod.rs
+++ b/optd/src/memo/mod.rs
@@ -237,3 +237,6 @@ pub trait Memo: Representative + Materialize + Sync + 'static {
         member_id: GoalMemberId,
     ) -> Result<bool, Self::MemoError>;
 }
+
+#[cfg(test)]
+mod fuzz;
\ No newline at end of file