diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index 234b56c..d32a44b 100644
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -475,6 +475,27 @@
         self.assertRaises(TypeError, self.type2test(b'abc').lstrip, 'b')
         self.assertRaises(TypeError, self.type2test(b'abc').rstrip, 'b')
 
+    def test_center(self):
+        # Fill character can be either bytes or bytearray (issue 12380)
+        b = self.type2test(b'abc')
+        for fill_type in (bytes, bytearray):
+            self.assertEqual(b.center(7, fill_type(b'-')),
+                             self.type2test(b'--abc--'))
+
+    def test_ljust(self):
+        # Fill character can be either bytes or bytearray (issue 12380)
+        b = self.type2test(b'abc')
+        for fill_type in (bytes, bytearray):
+            self.assertEqual(b.ljust(7, fill_type(b'-')),
+                             self.type2test(b'abc----'))
+
+    def test_rjust(self):
+        # Fill character can be either bytes or bytearray (issue 12380)
+        b = self.type2test(b'abc')
+        for fill_type in (bytes, bytearray):
+            self.assertEqual(b.rjust(7, fill_type(b'-')),
+                             self.type2test(b'----abc'))
+
     def test_ord(self):
         b = self.type2test(b'\0A\x7f\x80\xff')
         self.assertEqual([ord(b[i:i+1]) for i in range(len(b))],
diff --git a/Lib/test/test_getargs2.py b/Lib/test/test_getargs2.py
index 3d9c06a..768ea8d 100644
--- a/Lib/test/test_getargs2.py
+++ b/Lib/test/test_getargs2.py
@@ -294,6 +294,15 @@
             self.fail('TypeError should have been raised')
 
 class Bytes_TestCase(unittest.TestCase):
+    def test_c(self):
+        from _testcapi import getargs_c
+        self.assertRaises(TypeError, getargs_c, b'abc')  # len > 1
+        self.assertEqual(getargs_c(b'a'), b'a')
+        self.assertEqual(getargs_c(bytearray(b'a')), b'a')
+        self.assertRaises(TypeError, getargs_c, memoryview(b'a'))
+        self.assertRaises(TypeError, getargs_c, 's')
+        self.assertRaises(TypeError, getargs_c, None)
+
     def test_s(self):
         from _testcapi import getargs_s
         self.assertEqual(getargs_s('abc\xe9'), b'abc\xc3\xa9')