add 'transcode_file' helper method

python/CMDTEST_example.py

@@ -114,6 +114,17 @@ class TC_example(TestCase):
         with self.cmd("true") as c:
             pass
 
+    def test_09_encoding(self):
+        self.create_file("abc.txt", [
+            'detta är abc.txt',
+            'räksmörgås',
+            ' aaa',
+            ' bbb',
+            ' ccc',
+            ' ddd',
+        ], encoding='utf-16')
+        self.transcode_file('abc.txt', 'xxx.txt', src_encoding='utf-16', tgt_encoding='utf-32')
+
     def xxx_test_bool(self):
         with self.cmd("true") as c:
             c.exit_status(0)

python/cmdtest.py

@@ -357,6 +357,17 @@ class TestCase:
             else:
                 f.write(content)
 
+    def transcode_file(self, src_file, tgt_file=None, src_encoding='utf-8', tgt_encoding='utf-8'):
+        if tgt_file:
+            mkdir_for(tgt_file)
+        else:
+            tgt_file = src_file
+
+        with open(src_file, "r", encoding=src_encoding) as f:
+            data = f.read()
+        with open(tgt_file, "w", encoding=tgt_encoding) as f:
+            f.write(data)
+
     def cmd(self, cmdline):
         tmpdir = self.__tmpdir
         before = tmpdir.snapshot()