test(heap): add random test that exposes some faults

src/heap/vieter_heap.c

@@ -56,7 +56,7 @@ vieter_heap_error vieter_heap_pop(void **out, vieter_heap *heap) {
     return vieter_heap_empty;
   }
 
-  if (heap->tree->order == 0) {
+  if (heap->tree->order == 0 && heap->tree->ptr.next_tree == NULL) {
     *out = heap->tree->data;
     vieter_heap_tree_free(heap->tree);
     heap->tree = NULL;

src/heap/vieter_heap_tree.c

@@ -162,7 +162,7 @@ vieter_heap_node *vieter_heap_tree_pop(void **out, vieter_heap_node *tree) {
   *out = tree_to_pop->data;
 
   if (tree_to_pop->order == 0) {
-    vieter_heap_tree_free(tree);
+    vieter_heap_tree_free(tree_to_pop);
 
     return original_root;
   }
@@ -183,5 +183,10 @@ vieter_heap_node *vieter_heap_tree_pop(void **out, vieter_heap_node *tree) {
     tree = next_tree;
   }
 
-  return vieter_heap_tree_merge(original_root, previous_tree);
+  // original_root is zero if the heap only contained a single tree.
+  if (original_root != NULL) {
+    return vieter_heap_tree_merge(original_root, previous_tree);
+  } else {
+    return previous_tree;
+  }
 }

src/heap/vieter_heap_tree.h

@@ -9,28 +9,45 @@ typedef struct vieter_heap_node {
     void *data;
     struct vieter_heap_node *largest_order;
     union {
-        struct vieter_heap_node *next_tree;
+      // Roots point to next tree in the heap, other nodes point to their first
-        struct vieter_heap_node *next_largest_order;
+      // neighbour.
+      struct vieter_heap_node *next_tree;
+      struct vieter_heap_node *next_largest_order;
     } ptr;
     uint8_t order;
 } vieter_heap_node;
 
+/*
+ * Allocate an initialize a heap node object.
+ */
 vieter_heap_node *vieter_heap_node_init();
 
+/*
+ * Deallocate a node object.
+ */
 void vieter_heap_node_free(vieter_heap_node *node);
 
-/* vieter_heap_tree *vieter_heap_tree_init(vieter_heap_node *root, vieter_heap_tree *next, uint8_t order); */
-
 /*
- * Deallocate a tree object, along with its underlying tree structure.
+ * Deallocate a node's entire structure.
  */
 void vieter_heap_tree_free(vieter_heap_node *root);
 
+/*
+ * Given the roots of the smallest trees in two heaps, merge them into a single
+ * large heap.
+ */
 vieter_heap_node *vieter_heap_tree_merge(vieter_heap_node *root_a, vieter_heap_node *root_b);
 
+/*
+ * Given the roots of two trees of the same order, merge them into a heap of one
+ * order larger.
+ */
 vieter_heap_node *vieter_heap_tree_merge_same_order(vieter_heap_node *root_a,
                                                     vieter_heap_node *root_b);
 
+/*
+ * Remove the smallest element from the given heap.
+ */
 vieter_heap_node *vieter_heap_tree_pop(void **out, vieter_heap_node *root);
 
 #endif

test/heap/test_heap.c

@@ -1,6 +1,7 @@
 #include "acutest.h"
 #include "vieter_heap.h"
 #include "vieter_heap_tree.h"
+#include <stdlib.h>
 
 #define TEST_SIZE(heap, size) \
     TEST_CHECK(vieter_heap_size(heap) == size); \
@@ -76,10 +77,57 @@ void test_pop() {
     vieter_heap_free(heap);
 }
 
+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)) {
+        return 1;
+    } else {
+        return 0;
+    }
+}
+
+void test_pop_random() {
+    srand(0);
+
+    vieter_heap *heap = vieter_heap_init();
+
+    uint64_t *numbers = malloc(500 * sizeof(uint64_t));
+    uint64_t num;
+
+    for (uint64_t i = 0; i < 500; i++) {
+        num = rand();
+        vieter_heap_insert(heap, num, (void *)num);
+        TEST_SIZE(heap, i + 1);
+
+        numbers[i] = num;
+    }
+
+
+    qsort(numbers, 500, sizeof(uint64_t), uint64_t_compare);
+
+    void *data = NULL;
+
+    for (uint64_t i = 0; i < 500; i++) {
+        TEST_CHECK(vieter_heap_peek(&data, heap) == vieter_heap_ok);
+        TEST_CHECK(data == (void *)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);
+    }
+
+    vieter_heap_free(heap);
+    free(numbers);
+}
+
 TEST_LIST = {
     {"init", test_init},
     {"merge same order", test_merge_same_order},
     {"insert", test_insert},
     {"pop", test_pop},
+    {"pop random", test_pop_random},
     {NULL, NULL}
 };