issue-757: check data that was written before static BS group destruc…

…tion in local-emergency test (#2068)

cloud/blockstore/tests/loadtest/local-emergency/test.py

@@ -90,6 +90,13 @@ def __run_test(test_case):
     env.nbs.storage_config_patches = [storage_config_with_emergency_mode(backups_folder)]
     env.nbs.restart()
 
+    session.mount_volume()
+    data = session.read_blocks(100499, 3, "")
+    # check data (that was written) together with left & right neighborhood
+    assert data == [b''] + [b'\1' * 4096] + [b'']
+    # TODO: should not unmount volume to make emergency unexpected
+    session.unmount_volume()
+
     try:
         ret = run_test(
             "emergency-%s" % test_case.name,