tests/subsys/fs/nvs: extend entry delete test

Extended case for testing deletion of the first entry while
it is the most recent one.
This extension allow to reproduce issue #18813 and shows that
the bugfix works well.

Signed-off-by: Andrzej Puzdrowski <[email protected]>

Author: nvlsianpu

tests/subsys/fs/nvs/src/main.c

@@ -556,6 +556,18 @@ void test_delete(void)
 
 		zassert_true(len == sizeof(filling_id), "nvs_write failed: %d",
 			     len);
+
+		if (filling_id != 0) {
+			continue;
+		}
+
+		/* delete the first entry while it is the most recent one */
+		err = nvs_delete(&fs, filling_id);
+		zassert_true(err == 0,  "nvs_delete call failure: %d", err);
+
+		len = nvs_read(&fs, filling_id, &data_read, sizeof(data_read));
+		zassert_true(len == -ENOENT,
+			     "nvs_read shouldn't found the entry: %d", len);
 	}
 
 	/* delete existing entry */