dm: Add tests for the sandbox host driver

Add some unit tests for this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/py/tests/test_ut.py b/test/py/tests/test_ut.py
index 9d42390..bab8b97 100644
--- a/test/py/tests/test_ut.py
+++ b/test/py/tests/test_ut.py
@@ -7,6 +7,7 @@
 import pytest
 
 import u_boot_utils
+from tests import fs_helper
 
 def mkdir_cond(dirname):
     """Create a directory if it doesn't already exist
@@ -123,6 +124,11 @@
         u_boot_utils.run_and_log(
             u_boot_console, f'sfdisk {fn}', stdin=b'type=83')
 
+    fs_helper.mk_fs(u_boot_console.config, 'ext2', 0x200000, '2MB',
+                    use_src_dir=True)
+    fs_helper.mk_fs(u_boot_console.config, 'fat32', 0x100000, '1MB',
+                    use_src_dir=True)
+
 @pytest.mark.buildconfigspec('cmd_bootflow')
 def test_ut_dm_init_bootstd(u_boot_console):
     """Initialise data for bootflow tests"""