diff --git a/src/apps/testapps/testCompactCells.c b/src/apps/testapps/testCompactCells.c
index 94e1d01e8..b1ff58fea 100644
--- a/src/apps/testapps/testCompactCells.c
+++ b/src/apps/testapps/testCompactCells.c
@@ -91,6 +91,34 @@ SUITE(compactCells) {
         free(children);
     }
 
+    TEST(allRes1) {
+        const int64_t numRes0 = 122;
+        const int64_t numRes1 = 842;
+        H3Index *cells0 = calloc(numRes0, sizeof(H3Index));
+        H3Index *cells1 = calloc(numRes1, sizeof(H3Index));
+        H3Index *out = calloc(numRes1, sizeof(H3Index));
+
+        H3_EXPORT(getRes0Cells)(cells0);
+        t_assert(cells0[0] == 0x8001fffffffffff,
+                 "got expected first res0 cell");
+
+        t_assertSuccess(
+            H3_EXPORT(uncompactCells)(cells0, numRes0, cells1, numRes1, 1));
+
+        // Fails at compactCells.
+        // However:
+        //   Passes if numUncompacted <= 40
+        //   Fails  if numUncompacted >= 41.
+        int64_t numUncompacted = numRes1;
+        t_assertSuccess(H3_EXPORT(compactCells)(cells1, out, numUncompacted));
+
+        // TODO: check that output matches cells0
+
+        free(cells0);
+        free(cells1);
+        free(out);
+    }
+
     TEST(res0) {
         int hexCount = NUM_BASE_CELLS;