diff --git a/src/heap/vieter_heap.c b/src/heap/vieter_heap.c
index f6d3eab..45f9e01 100644
--- a/src/heap/vieter_heap.c
+++ b/src/heap/vieter_heap.c
@@ -56,14 +56,6 @@ vieter_heap_error vieter_heap_pop(void **out, vieter_heap *heap) {
     return vieter_heap_empty;
   }
 
-  if (heap->tree->order == 0 && heap->tree->ptr.next_tree == NULL) {
-    *out = heap->tree->data;
-    vieter_heap_tree_free(heap->tree);
-    heap->tree = NULL;
-
-    return vieter_heap_ok;
-  }
-
   heap->tree = vieter_heap_tree_pop(out, heap->tree);
 
   return vieter_heap_ok;
diff --git a/src/heap/vieter_heap_tree.c b/src/heap/vieter_heap_tree.c
index 56907a8..ff1ee66 100644
--- a/src/heap/vieter_heap_tree.c
+++ b/src/heap/vieter_heap_tree.c
@@ -167,6 +167,9 @@ vieter_heap_node *vieter_heap_tree_pop(void **out, vieter_heap_node *tree) {
     return original_root;
   }
 
+  // Each child has a pointer to its sibling with the next largest order. If we
+  // want to convert this list of children into their own tree, these pointers
+  // have to be reversed.
   previous_tree = tree_to_pop->largest_order;
   vieter_heap_node_free(tree_to_pop);
 
diff --git a/test/heap/test_heap.c b/test/heap/test_heap.c
index e136d87..ad73b8c 100644
--- a/test/heap/test_heap.c
+++ b/test/heap/test_heap.c
@@ -5,7 +5,7 @@
 
 #define TEST_SIZE(heap, size) \
     TEST_CHECK(vieter_heap_size(heap) == size); \
-    TEST_MSG("Size: %zu", vieter_heap_size(heap))
+    TEST_MSG("Size: %zu, expected: %lu", vieter_heap_size(heap), (uint64_t)size)
 
 void test_init() {
     vieter_heap *heap = vieter_heap_init();
@@ -14,25 +14,6 @@ void test_init() {
     vieter_heap_free(heap);
 }
 
-void test_merge_same_order() {
-    vieter_heap_node *root_a = vieter_heap_node_init();
-    root_a->key = 1;
-    root_a->order = 0;
-
-    vieter_heap_node *root_b = vieter_heap_node_init();
-    root_b->key = 2;
-    root_b->order = 0;
-
-    vieter_heap_node *merged = vieter_heap_tree_merge_same_order(root_a, root_b);
-
-    TEST_CHECK(merged == root_a);
-    TEST_CHECK(merged->key == 1);
-    TEST_CHECK(merged->largest_order == root_b);
-    TEST_CHECK(merged->ptr.next_largest_order == NULL);
-
-    vieter_heap_tree_free(merged);
-}
-
 void test_insert() {
     vieter_heap *heap = vieter_heap_init();
     TEST_SIZE(heap, 0);
@@ -52,6 +33,36 @@ void test_insert() {
     vieter_heap_free(heap);
 }
 
+void test_insert_random() {
+    srand(1);
+
+    vieter_heap *heap = vieter_heap_init();
+    TEST_SIZE(heap, 0);
+
+    uint64_t num = rand();
+    uint64_t smallest = num;
+
+    void *data = NULL;
+
+    for (uint64_t i = 0; i < 5000; i++) {
+        vieter_heap_insert(heap, num, (void *)num);
+        TEST_SIZE(heap, i + 1);
+
+        if (num < smallest) {
+            smallest = num;
+        }
+
+        TEST_CHECK(vieter_heap_peek(&data, heap) == vieter_heap_ok);
+        TEST_CHECK(data == (void *)smallest);
+
+        data = NULL;
+
+        num = rand();
+    }
+
+    vieter_heap_free(heap);
+}
+
 void test_pop() {
     vieter_heap *heap = vieter_heap_init();
     TEST_SIZE(heap, 0);
@@ -80,7 +91,7 @@ void test_pop() {
 int uint64_t_compare(const void *a, const void *b) {
     if ((*(uint64_t *)a) < (*(uint64_t *)b)) {
         return -1;
-    } else if ((*(uint64_t *)a) < (*(uint64_t *)b)) {
+    } else if ((*(uint64_t *)a) > (*(uint64_t *)b)) {
         return 1;
     } else {
         return 0;
@@ -88,14 +99,16 @@ int uint64_t_compare(const void *a, const void *b) {
 }
 
 void test_pop_random() {
+    const uint64_t n = 29;
+
     srand(0);
 
     vieter_heap *heap = vieter_heap_init();
 
-    uint64_t *numbers = malloc(500 * sizeof(uint64_t));
+    uint64_t *numbers = malloc(n * sizeof(uint64_t));
     uint64_t num;
 
-    for (uint64_t i = 0; i < 500; i++) {
+    for (uint64_t i = 0; i < n; i++) {
         num = rand();
         vieter_heap_insert(heap, num, (void *)num);
         TEST_SIZE(heap, i + 1);
@@ -104,19 +117,19 @@ void test_pop_random() {
     }
 
 
-    qsort(numbers, 500, sizeof(uint64_t), uint64_t_compare);
+    qsort(numbers, n, sizeof(uint64_t), uint64_t_compare);
 
     void *data = NULL;
 
-    for (uint64_t i = 0; i < 500; i++) {
+    for (uint64_t i = 0; i < n; i++) {
         TEST_CHECK(vieter_heap_peek(&data, heap) == vieter_heap_ok);
-        TEST_CHECK(data == (void *)numbers[i]);
+        TEST_CHECK_(data == (void *)numbers[i], "peek %lx == %lx", (uint64_t)data, numbers[i]);
 
         data = NULL;
 
         TEST_CHECK(vieter_heap_pop(&data, heap) == vieter_heap_ok);
-        TEST_CHECK(data == (void *)numbers[i]);
-        TEST_SIZE(heap, (uint64_t)500 - i - 1);
+        TEST_CHECK_(data == (void *)numbers[i], "pop %lx == %lx", (uint64_t)data, numbers[i]);
+        TEST_SIZE(heap, n - i - 1);
     }
 
     vieter_heap_free(heap);
@@ -125,8 +138,8 @@ void test_pop_random() {
 
 TEST_LIST = {
     {"init", test_init},
-    {"merge same order", test_merge_same_order},
     {"insert", test_insert},
+    {"insert random", test_insert_random},
     {"pop", test_pop},
     {"pop random", test_pop_random},
     {NULL, NULL}
diff --git a/test/heap/test_merge.c b/test/heap/test_merge.c
new file mode 100644
index 0000000..10053f2
--- /dev/null
+++ b/test/heap/test_merge.c
@@ -0,0 +1,28 @@
+#include "acutest.h"
+#include "vieter_heap.h"
+#include "vieter_heap_tree.h"
+#include <stdlib.h>
+
+void test_merge_same_order() {
+    vieter_heap_node *root_a = vieter_heap_node_init();
+    root_a->key = 1;
+    root_a->order = 0;
+
+    vieter_heap_node *root_b = vieter_heap_node_init();
+    root_b->key = 2;
+    root_b->order = 0;
+
+    vieter_heap_node *merged = vieter_heap_tree_merge_same_order(root_a, root_b);
+
+    TEST_CHECK(merged == root_a);
+    TEST_CHECK(merged->key == 1);
+    TEST_CHECK(merged->largest_order == root_b);
+    TEST_CHECK(merged->ptr.next_largest_order == NULL);
+
+    vieter_heap_tree_free(merged);
+}
+
+TEST_LIST = {
+    {"merge same order", test_merge_same_order},
+    {NULL, NULL}
+};