diff --git a/test/heapTest.mo b/test/heapTest.mo
index 6b3b172a..49f81845 100644
--- a/test/heapTest.mo
+++ b/test/heapTest.mo
@@ -1,51 +1,106 @@
-import H "mo:base/Heap";
-import I "mo:base/Iter";
-import O "mo:base/Option";
-import Int "mo:base/Int";
-
-let order = Int.compare;
-
-do {
-  var pq = H.Heap<Int>(order);
-  for (i in I.revRange(100, 0)) {
-    pq.put(i);
-    let x = pq.peekMin();
-    assert (O.unwrap(x) == i)
-  };
-  for (i in I.range(0, 100)) {
-    pq.put(i);
-    let x = pq.peekMin();
-    assert (O.unwrap(x) == 0)
-  };
-  for (i in I.range(0, 100)) {
-    pq.deleteMin();
-    let x = pq.peekMin();
-    pq.deleteMin();
-    assert (O.unwrap(x) == i)
-  };
-  O.assertNull(pq.peekMin())
-};
+import Heap "mo:base/Heap";
+import Iter "mo:base/Iter";
+import Option "mo:base/Option";
+import Nat "mo:base/Nat";
+import Stack "mo:base/Stack";
+
+import Suite "mo:matchers/Suite";
+import T "mo:matchers/Testable";
+import M "mo:matchers/Matchers";
 
-// fromIter
-do {
-  do {
-    let iter = [5, 10, 9, 7, 3, 8, 1, 0, 2, 4, 6].vals();
-    let pq = H.fromIter<Int>(iter, order);
-    for (i in I.range(0, 10)) {
-      let x = pq.peekMin();
-      assert (O.unwrap(x) == i);
-      pq.deleteMin()
-    };
-    O.assertNull(pq.peekMin())
-  };
-
-  do {
-    let pq = H.fromIter<Int>([].vals(), order);
-    O.assertNull(pq.peekMin())
-  };
-
-  do {
-    let pq = H.fromIter<Int>([100].vals(), order);
-    assert (O.unwrap(pq.peekMin()) == 100)
+// FIXME put this in the Heap module in a separate PR
+func toIter<X>(heap : Heap.Heap<X>) : Iter.Iter<X> {
+  let stack = Stack.Stack<Heap.Tree<X>>();
+  stack.push(heap.share());
+  func next() : ?X {
+    switch (stack.pop()) {
+      case (null) {
+        null
+      };
+      // FIXME this iterator is not in order
+      case (?(_, element, left, right)) {
+        stack.push(tree.left);
+        stack.push(tree.right);
+        ?element
+      }
+    }
   }
-}
+};
+
+// Test data
+func newEmptyHeap() : Heap.Heap<Nat> {
+  Heap.Heap<Nat>(Nat.compare)
+};
+
+func newSingletonHeap() : Heap.Heap<Nat> {
+  let heap = newEmptyHeap();
+  heap.put(1);
+  heap
+};
+
+func newHeap() : Heap.Heap<Nat> {
+  let heap = newEmptyHeap();
+  heap.put(1);
+  heap.put(2);
+  heap.put(3);
+  heap
+};
+
+// Test suite
+let suite = Suite.suite(
+  "Heap",
+  [
+    Suite.test(
+      "init",
+      Array.freeze(Array.init<Int>(3, 4)),
+      M.equals(T.array<Int>(T.intTestable, [4, 4, 4]))
+    )
+  ]
+);
+
+Suite.run(suite);
+
+// do {
+//   var pq = H.Heap<Int>(order);
+//   for (i in I.revRange(100, 0)) {
+//     pq.put(i);
+//     let x = pq.peekMin();
+//     assert (O.unwrap(x) == i)
+//   };
+//   for (i in I.range(0, 100)) {
+//     pq.put(i);
+//     let x = pq.peekMin();
+//     assert (O.unwrap(x) == 0)
+//   };
+//   for (i in I.range(0, 100)) {
+//     pq.deleteMin();
+//     let x = pq.peekMin();
+//     pq.deleteMin();
+//     assert (O.unwrap(x) == i)
+//   };
+//   O.assertNull(pq.peekMin())
+// };
+
+// // fromIter
+// do {
+//   do {
+//     let iter = [5, 10, 9, 7, 3, 8, 1, 0, 2, 4, 6].vals();
+//     let pq = H.fromIter<Int>(iter, order);
+//     for (i in I.range(0, 10)) {
+//       let x = pq.peekMin();
+//       assert (O.unwrap(x) == i);
+//       pq.deleteMin()
+//     };
+//     O.assertNull(pq.peekMin())
+//   };
+
+//   do {
+//     let pq = H.fromIter<Int>([].vals(), order);
+//     O.assertNull(pq.peekMin())
+//   };
+
+//   do {
+//     let pq = H.fromIter<Int>([100].vals(), order);
+//     assert (O.unwrap(pq.peekMin()) == 100)
+//   }
+// }