--- /dev/null
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "mempool.h"
+#include "random-util.h"
+#include "tests.h"
+
+struct element {
+ uint64_t value;
+};
+
+DEFINE_MEMPOOL(test_mempool, struct element, 8);
+
+TEST(mempool_trim) {
+
+#define NN 4000
+ struct element *a[NN];
+ size_t n_freed = 0;
+
+ assert_se(!test_mempool.first_pool);
+ assert_se(!test_mempool.freelist);
+
+ mempool_trim(&test_mempool);
+
+ for (size_t i = 0; i < NN; i++) {
+ assert_se(a[i] = mempool_alloc_tile(&test_mempool));
+ a[i]->value = i;
+ }
+
+ mempool_trim(&test_mempool);
+
+ /* free up to one third randomly */
+ size_t x = 0;
+ for (size_t i = 0; i < NN/3; i++) {
+ x = (x + random_u64()) % ELEMENTSOF(a);
+ assert_se(!a[x] || a[x]->value == x);
+
+ if (a[x])
+ n_freed ++;
+
+ a[x] = mempool_free_tile(&test_mempool, a[x]);
+ }
+
+ mempool_trim(&test_mempool);
+
+ /* free definitely at least one third */
+ for (size_t i = 2; i < NN; i += 3) {
+ assert_se(!a[i] || a[i]->value == i);
+ if (a[i])
+ n_freed ++;
+ a[i] = mempool_free_tile(&test_mempool, a[i]);
+ }
+
+ mempool_trim(&test_mempool);
+
+ /* Allocate another set of tiles, which will fill up the free list and allocate some new tiles */
+ struct element *b[NN];
+ for (size_t i = 0; i < NN; i++) {
+ assert_se(b[i] = mempool_alloc_tile(&test_mempool));
+ b[i]->value = ~(uint64_t) i;
+ }
+
+ mempool_trim(&test_mempool);
+
+ /* free everything from the original set*/
+
+ for (size_t i = 0; i < NN; i += 1) {
+ assert_se(!a[i] || a[i]->value == i);
+ if (a[i])
+ n_freed ++;
+ a[i] = mempool_free_tile(&test_mempool, a[i]);
+ }
+
+ mempool_trim(&test_mempool);
+
+ /* and now everything from the second set too */
+
+ for (size_t i = 0; i < NN; i += 1) {
+ assert_se(!b[i] || b[i]->value == ~(uint64_t) i);
+ if (b[i])
+ n_freed ++;
+ b[i] = mempool_free_tile(&test_mempool, b[i]);
+ }
+
+ assert_se(n_freed == NN * 2);
+
+ mempool_trim(&test_mempool);
+
+ assert_se(!test_mempool.first_pool);
+ assert_se(!test_mempool.freelist);
+}
+
+DEFINE_TEST_MAIN(LOG_DEBUG);