restructure a bit to not rely on test case execution ordering

add test case for bug #482460

Lib/test/test_dumbdbm.py

@@ -30,11 +30,8 @@ class DumbDBMTestCase(unittest.TestCase):
 
     def __init__(self, *args):
         unittest.TestCase.__init__(self, *args)
-        self._dkeys = self._dict.keys()
-        self._dkeys.sort()
 
     def test_dumbdbm_creation(self):
-        _delete_files()
         f = dumbdbm.open(_fname, 'c')
         self.assertEqual(f.keys(), [])
         for key in self._dict:
@@ -43,32 +40,59 @@ class DumbDBMTestCase(unittest.TestCase):
         f.close()
 
     def test_dumbdbm_modification(self):
+        self.init_db()
         f = dumbdbm.open(_fname, 'w')
         self._dict['g'] = f['g'] = "indented"
         self.read_helper(f)
         f.close()
 
     def test_dumbdbm_read(self):
+        self.init_db()
         f = dumbdbm.open(_fname, 'r')
         self.read_helper(f)
         f.close()
 
     def test_dumbdbm_keys(self):
+        self.init_db()
         f = dumbdbm.open(_fname)
         keys = self.keys_helper(f)
         f.close()
 
+    def test_write_write_read(self):
+        # test for bug #482460
+        f = dumbdbm.open(_fname)
+        f['1'] = 'hello'
+        f['1'] = 'hello2'
+        f.close()
+        f = dumbdbm.open(_fname)
+        self.assertEqual(f['1'], 'hello2')
+        f.close()
+
     def read_helper(self, f):
         keys = self.keys_helper(f)
         for key in self._dict:
             self.assertEqual(self._dict[key], f[key])
 
+    def init_db(self):
+        f = dumbdbm.open(_fname, 'w')
+        for k in self._dict:
+            f[k] = self._dict[k]
+        f.close()
+
     def keys_helper(self, f):
         keys = f.keys()
         keys.sort()
-        self.assertEqual(keys, self._dkeys)
+        dkeys = self._dict.keys()
+        dkeys.sort()
+        self.assertEqual(keys, dkeys)
         return keys
 
+    def tearDown(self):
+        _delete_files()
+
+    def setUp(self):
+        _delete_files()
+
 def test_main():
     try:
         test_support.run_unittest(DumbDBMTestCase)