[gparted] Add clearing FS label to CreateAndWriteLabel unit test

[Curtis Gedak <gedakc src gnome org>]

commit a46c0cbe8052aa2ef4521dea4db08f2dc71a80ea
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Mon Jun 20 20:47:38 2022 +0100

    Add clearing FS label to CreateAndWriteLabel unit test
    
    For FAT16/32 and XFS file systems clearing the label uses different
    command options and code path in file system specific ::write_label()
    method.  Therefore extend this unit test to also test clearing the
    label.

 tests/test_SupportedFileSystems.cc | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
---
diff --git a/tests/test_SupportedFileSystems.cc b/tests/test_SupportedFileSystems.cc
index f08b29b8..8b4d44a6 100644
--- a/tests/test_SupportedFileSystems.cc
+++ b/tests/test_SupportedFileSystems.cc
@@ -596,7 +596,11 @@ TEST_P(SupportedFileSystemsTest, CreateAndWriteLabel)
        m_partition.set_filesystem_label("FIRST");
        ASSERT_TRUE(m_fs_object->create(m_partition, m_operation_detail)) << m_operation_detail;
 
-       // Test writing a label is successful.
+       // Test clearing the label is successful.
+       m_partition.set_filesystem_label("");
+       ASSERT_TRUE(m_fs_object->write_label(m_partition, m_operation_detail)) << m_operation_detail;
+
+       // Test writing the label is successful.
        m_partition.set_filesystem_label("SECOND");
        ASSERT_TRUE(m_fs_object->write_label(m_partition, m_operation_detail)) << m_operation_detail;
 }