diff --git a/tests/test_array.c b/tests/test_array.c
index aeded71179df04d1bb7cd0b336cd780beeda1124..5151a545fa76473daf87480fa8e8be7913c0885a 100644
--- a/tests/test_array.c
+++ b/tests/test_array.c
@@ -49,12 +49,54 @@ static void test_array(void **state)
 	array_clear(arr);
 }
 
+/** Reservation through tracked memory allocator. */
+static int test_reserve(void *baton, char **mem, size_t elm_size, size_t want, size_t *have)
+{
+	if (want > *have) {
+		void *new_mem = mm_alloc(baton, elm_size * want);
+		if (*mem != NULL) {
+			memcpy(new_mem, *mem, (*have) * elm_size);
+			mm_free(baton, *mem);
+		}
+		*mem = new_mem;
+		*have = want;
+	}
+
+	return 0;
+}
+
+/** Reservation through fake memory allocator. */
+static int fake_reserve(void *baton, char **mem, size_t elm_size, size_t want, size_t *have)
+{
+	return -1;
+}
+
+static void test_array_mm(void **state)
+{
+	array_t(int) arr;
+	array_init(arr);
+
+	/* Reserve using fake memory allocator. */
+	assert_false(array_reserve_mm(arr, 5, fake_reserve, NULL) >= 0);
+
+	/* Reserve capacity and fill. */
+	assert_true(array_reserve_mm(arr, 100, test_reserve, &global_mm) >= 0);
+	for (unsigned i = 0; i < 100; ++i) {
+		int ret = array_push(arr, i);
+		assert_true(ret >= 0);
+	}
+
+	array_clear_mm(arr, mm_free, &global_mm);
+
+}
+
 int main(void)
 {
 	test_mm_ctx_init(&global_mm);
 
 	const UnitTest tests[] = {
 		unit_test(test_array),
+		unit_test(test_array_mm)
 	};
 
 	return run_tests(tests);
diff --git a/tests/test_set.c b/tests/test_set.c
index 3f51abe7f7472d8cebea041440a8188e583e2bbd..b1aa791f6d191d9001faeca6f13fa12fff94aafe 100644
--- a/tests/test_set.c
+++ b/tests/test_set.c
@@ -131,7 +131,7 @@ static void test_delete_all(void **state)
 }
 
 /* Fake allocator */
-static void *fake_malloc(size_t s, void *b) { return NULL; }
+static void *fake_malloc(void *b, size_t s) { return NULL; }
 static void test_allocator(void **state)
 {
 	set_t set = set_make();
@@ -216,4 +216,4 @@ int main(int argc, char **argv)
 	};
 
 	return run_group_tests(tests);
-}
\ No newline at end of file
+}