diff --git a/source/tests/ftl/write_page_desc.c b/source/tests/ftl/write_page_desc.c
new file mode 100644
index 0000000..37520ac
--- /dev/null
+++ b/source/tests/ftl/write_page_desc.c
@@ -0,0 +1,258 @@
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <setjmp.h>
+
+#include <cmocka.h>
+
+#include <bitops.h>
+#include <flash.h>
+#include <ftl.h>
+#include <macros.h>
+
+int write_page_desc(struct ftl_map *map,
+	struct ftl_page_desc *page_desc);
+
+static int test_setup(void **state)
+{
+	struct ftl_map *map;
+
+	if (!(map = test_malloc(sizeof(*map))))
+		return -1;
+
+	map->log2_pages_per_group = ilog2(16);
+	map->log2_groups_per_block = ilog2(1);
+	map->log2_page_size = ilog2(4 * KIB);
+	map->nblocks = 4;
+	map->epoch = 0;
+
+	*state = map;
+
+	return 0;
+}
+
+static int test_teardown(void **state)
+{
+	struct ftl_map *map = *state;
+
+	test_free(map);
+
+	return 0;
+}
+
+static void test_write_page_desc1(void **state)
+{
+	struct ftl_map *map = *state;
+	struct ftl_page_desc page_desc, ret_page_desc;
+	size_t ret;
+
+	expect_value(__wrap_flash_is_erased, addr, 16 - 1);
+	expect_value(__wrap_flash_is_erased, len, 1);
+	will_return(__wrap_flash_is_erased, 0);
+
+	expect_value(__wrap_flash_write, addr, (16 - 1) * 4 * KIB +
+		sizeof(struct ftl_page_group));
+	expect_value(__wrap_flash_write, len, sizeof page_desc);
+	will_return(__wrap_flash_write, sizeof page_desc);
+	will_return(__wrap_flash_write, &ret_page_desc);
+
+	map->head = 0;
+
+	ret = write_page_desc(map, &page_desc);
+
+	assert_int_equal(ret, 0);
+	assert_int_equal(map->root, 0);
+	assert_int_equal(map->head, 1);
+	assert_int_equal(map->epoch, 0);
+	assert_memory_equal(ret_page_desc.magic, "page", 4);
+}
+
+static void test_write_page_desc2(void **state)
+{
+	struct ftl_map *map = *state;
+	struct ftl_page_desc page_desc, ret_page_desc;
+	size_t ret;
+
+	expect_value(__wrap_flash_is_erased, addr, 16 - 1);
+	expect_value(__wrap_flash_is_erased, len, 1);
+	will_return(__wrap_flash_is_erased, 0);
+
+	expect_value(__wrap_flash_write, addr, (16 - 1) * 4 * KIB +
+		sizeof(struct ftl_page_group) + 14 * sizeof(struct ftl_page_desc));
+	expect_value(__wrap_flash_write, len, sizeof page_desc);
+	will_return(__wrap_flash_write, sizeof page_desc);
+	will_return(__wrap_flash_write, &ret_page_desc);
+
+	map->head = 14;
+
+	ret = write_page_desc(map, &page_desc);
+
+	assert_int_equal(ret, 0);
+	assert_int_equal(map->root, 14);
+	assert_int_equal(map->head, 16);
+	assert_int_equal(map->epoch, 0);
+	assert_memory_equal(ret_page_desc.magic, "page", 4);
+}
+
+static void test_write_page_desc3(void **state)
+{
+	struct ftl_map *map = *state;
+	struct ftl_page_desc page_desc, ret_page_desc;
+	size_t ret;
+
+	expect_value(__wrap_flash_is_erased, addr, 2 * 16 - 1);
+	expect_value(__wrap_flash_is_erased, len, 1);
+	will_return(__wrap_flash_is_erased, 0);
+
+	expect_value(__wrap_flash_write, addr, (2 * 16 - 1) * 4 * KIB +
+		sizeof(struct ftl_page_group));
+	expect_value(__wrap_flash_write, len, sizeof page_desc);
+	will_return(__wrap_flash_write, sizeof page_desc);
+	will_return(__wrap_flash_write, &ret_page_desc);
+
+	map->head = 16;
+
+	ret = write_page_desc(map, &page_desc);
+
+	assert_int_equal(ret, 0);
+	assert_int_equal(map->root, 16);
+	assert_int_equal(map->head, 17);
+	assert_int_equal(map->epoch, 0);
+	assert_memory_equal(ret_page_desc.magic, "page", 4);
+}
+
+static void test_write_page_desc4(void **state)
+{
+	struct ftl_map *map = *state;
+	struct ftl_page_desc page_desc, ret_page_desc;
+	size_t ret;
+
+	expect_value(__wrap_flash_is_erased, addr, 2 * 16 - 1);
+	expect_value(__wrap_flash_is_erased, len, 1);
+	will_return(__wrap_flash_is_erased, 0);
+
+	expect_value(__wrap_flash_write, addr, (2 * 16 - 1) * 4 * KIB +
+		sizeof(struct ftl_page_group) + 14 * sizeof(struct ftl_page_desc));
+	expect_value(__wrap_flash_write, len, sizeof page_desc);
+	will_return(__wrap_flash_write, sizeof page_desc);
+	will_return(__wrap_flash_write, &ret_page_desc);
+
+	map->head = 30;
+
+	ret = write_page_desc(map, &page_desc);
+
+	assert_int_equal(ret, 0);
+	assert_int_equal(map->root, 30);
+	assert_int_equal(map->head, 32);
+	assert_int_equal(map->epoch, 0);
+	assert_memory_equal(ret_page_desc.magic, "page", 4);
+}
+
+static void test_write_page_desc5(void **state)
+{
+	struct ftl_map *map = *state;
+	struct ftl_page_desc page_desc, ret_page_desc;
+	size_t ret;
+
+	expect_value(__wrap_flash_is_erased, addr, 3 * 16 - 1);
+	expect_value(__wrap_flash_is_erased, len, 1);
+	will_return(__wrap_flash_is_erased, 0);
+
+	expect_value(__wrap_flash_write, addr, (3 * 16 - 1) * 4 * KIB +
+		sizeof(struct ftl_page_group));
+	expect_value(__wrap_flash_write, len, sizeof page_desc);
+	will_return(__wrap_flash_write, sizeof page_desc);
+	will_return(__wrap_flash_write, &ret_page_desc);
+
+	map->head = 32;
+
+	ret = write_page_desc(map, &page_desc);
+
+	assert_int_equal(ret, 0);
+	assert_int_equal(map->root, 32);
+	assert_int_equal(map->head, 33);
+	assert_int_equal(map->epoch, 0);
+	assert_memory_equal(ret_page_desc.magic, "page", 4);
+}
+
+static void test_epoch_wraparound(void **state)
+{
+	struct ftl_map *map = *state;
+	struct ftl_page_desc page_desc, ret_page_desc;
+	size_t ret;
+
+	expect_value(__wrap_flash_is_erased, addr, 4 * 16 - 1);
+	expect_value(__wrap_flash_is_erased, len, 1);
+	will_return(__wrap_flash_is_erased, 0);
+
+	expect_value(__wrap_flash_write, addr, (4 * 16 - 1) * 4 * KIB +
+		sizeof(struct ftl_page_group) + 14 * sizeof(struct ftl_page_desc));
+	expect_value(__wrap_flash_write, len, sizeof page_desc);
+	will_return(__wrap_flash_write, sizeof page_desc);
+	will_return(__wrap_flash_write, &ret_page_desc);
+
+	map->head = 62;
+
+	ret = write_page_desc(map, &page_desc);
+
+	assert_int_equal(ret, 0);
+	assert_int_equal(map->root, 62);
+	assert_int_equal(map->head, 0);
+	assert_int_equal(map->epoch, 1);
+	assert_memory_equal(ret_page_desc.magic, "page", 4);
+}
+
+static void test_group_header(void **state)
+{
+	struct ftl_map *map = *state;
+	struct ftl_page_group ret_group;
+	struct ftl_page_desc page_desc, ret_page_desc;
+	size_t ret;
+
+	expect_value(__wrap_flash_is_erased, addr, 16 - 1);
+	expect_value(__wrap_flash_is_erased, len, 1);
+	will_return(__wrap_flash_is_erased, 1);
+
+	expect_value(__wrap_flash_write, addr, (16 - 1) * 4 * KIB);
+	expect_value(__wrap_flash_write, len, sizeof ret_group);
+	will_return(__wrap_flash_write, sizeof ret_group);
+	will_return(__wrap_flash_write, &ret_group);
+
+	expect_value(__wrap_flash_write, addr, (16 - 1) * 4 * KIB +
+		sizeof(struct ftl_page_group));
+	expect_value(__wrap_flash_write, len, sizeof page_desc);
+	will_return(__wrap_flash_write, sizeof page_desc);
+	will_return(__wrap_flash_write, &ret_page_desc);
+
+	map->head = 0;
+	map->epoch = 0;
+
+	ret = write_page_desc(map, &page_desc);
+
+	assert_int_equal(ret, 0);
+	assert_int_equal(map->root, 0);
+	assert_int_equal(map->head, 1);
+	assert_int_equal(map->epoch, 0);
+
+	assert_memory_equal(ret_group.magic, "FTL", 3);
+	assert_int_equal(ret_group.epoch, map->epoch);
+
+	assert_memory_equal(ret_page_desc.magic, "page", 4);
+}
+
+int test_write_page_desc(void)
+{
+	const struct CMUnitTest tests[] = {
+		{ "write_page_desc: head=0", test_write_page_desc1, NULL, NULL, NULL },
+		{ "write_page_desc: head=14", test_write_page_desc2, NULL, NULL, NULL },
+		{ "write_page_desc: head=16", test_write_page_desc3, NULL, NULL, NULL },
+		{ "write_page_desc: head=30", test_write_page_desc4, NULL, NULL, NULL },
+		{ "write_page_desc: head=32", test_write_page_desc5, NULL, NULL, NULL },
+		{ "write_page_desc: epoch wraparound", test_epoch_wraparound, NULL, NULL, NULL },
+		{ "write_page_desc: group header", test_group_header, NULL, NULL, NULL },
+	};
+
+	return cmocka_run_group_tests_name("write_page_desc", tests, test_setup,
+		test_teardown);
+}