Fix bug with the test helper method

Author: Jlalond

lldb/test/API/functionalities/process_save_core_minidump/TestProcessSaveCoreMinidumpYaml.py

@@ -7,7 +7,6 @@
 from lldbsuite.test.decorators import *
 from lldbsuite.test.lldbtest import *
 from lldbsuite.test import lldbutil
-from dataclass import dataclass
 
 
 class AddressRange:
@@ -52,10 +51,10 @@ def validate_regions_saved_correctly(
         # Validate we can't read the original_region
         core_process.ReadMemory(
             expected_invalid_region.begin,
-            expected_invalid_region.end - expected_invalid_region.end,
+            expected_invalid_region.end - expected_invalid_region.begin,
             error,
         )
-        self.assertTrue(error.Success(), error.GetCString())
+        self.assertTrue(error.Fail(), error.GetCString())
 
     def test_saving_sub_memory_range(self):
         """