diff --git a/src/lib.rs b/src/lib.rs
index ed4f414..359ce52 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -840,4 +840,4 @@ impl IndexMut<PointId> for Vec<ZeroNode> {
 /// The parameter `M` from the paper
 ///
 /// This should become a generic argument to `Hnsw` when possible.
-const M: usize = 12;
+const M: usize = 6;
diff --git a/tests/all.rs b/tests/all.rs
index be2a60a..9bdefc3 100644
--- a/tests/all.rs
+++ b/tests/all.rs
@@ -4,7 +4,7 @@ use ordered_float::OrderedFloat;
 use rand::rngs::{StdRng, ThreadRng};
 use rand::{Rng, SeedableRng};
 
-use instant_distance::{Hnsw, Point as _, PointId, Search};
+use instant_distance::{Builder, Heuristic, Hnsw, Point as _, PointId, Search};
 
 #[test]
 fn basic() {
@@ -24,10 +24,21 @@ fn basic() {
 }
 
 #[test]
-fn randomized() {
-    let seed = ThreadRng::default().gen::<u64>();
-    println!("seed {}", seed);
+fn random_heuristic() {
+    let (seed, recall) = randomized(Builder::default().select_heuristic(Heuristic::default()));
+    println!("heuristic (seed = {}) recall = {}", seed, recall);
+    assert!(recall > 98, "expected at least 98, got {}", recall);
+}
 
+#[test]
+fn random_simple() {
+    let (seed, recall) = randomized(Builder::default());
+    println!("simple (seed = {}) recall = {}", seed, recall);
+    assert!(recall > 90, "expected at least 90, got {}", recall);
+}
+
+fn randomized(builder: Builder) -> (u64, usize) {
+    let seed = ThreadRng::default().gen::<u64>();
     let mut rng = StdRng::seed_from_u64(seed);
     let points = (0..1024)
         .into_iter()
@@ -35,8 +46,6 @@ fn randomized() {
         .collect::<Vec<_>>();
 
     let query = Point(rng.gen(), rng.gen());
-    println!("query: {:?}", query);
-
     let mut nearest = Vec::with_capacity(256);
     for (i, p) in points.iter().enumerate() {
         nearest.push((OrderedFloat::from(query.distance(p)), i));
@@ -46,10 +55,7 @@ fn randomized() {
         }
     }
 
-    let (hnsw, pids) = Hnsw::<Point>::builder()
-        .seed(seed)
-        .select_heuristic(Default::default())
-        .build(&points);
+    let (hnsw, pids) = builder.seed(seed).build(&points);
     let mut search = Search::default();
     let mut results = vec![PointId::default(); 100];
     let found = hnsw.search(&query, &mut results, &mut search);
@@ -62,10 +68,7 @@ fn randomized() {
         .map(|(_, i)| pids[*i])
         .collect::<HashSet<_>>();
     let found = results.into_iter().take(found).collect::<HashSet<_>>();
-
-    let recall = forced.intersection(&found).count();
-    println!("{} matched", recall);
-    assert!(recall > 90);
+    (seed, forced.intersection(&found).count())
 }
 
 #[derive(Clone, Copy, Debug)]