Issue #18829: csv.Dialect() now checks type for delimiter, escapechar and
quotechar fields.  Original patch by Vajrasky Kok.
diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py
index 479ebd9..f1d14b9 100644
--- a/Lib/test/test_csv.py
+++ b/Lib/test/test_csv.py
@@ -747,6 +747,7 @@
             lineterminator = '\r\n'
             quoting = csv.QUOTE_NONE
         d = mydialect()
+        self.assertEqual(d.quoting, csv.QUOTE_NONE)
 
         mydialect.quoting = None
         self.assertRaises(csv.Error, mydialect)
@@ -755,12 +756,21 @@
         mydialect.quoting = csv.QUOTE_ALL
         mydialect.quotechar = '"'
         d = mydialect()
+        self.assertEqual(d.quoting, csv.QUOTE_ALL)
+        self.assertEqual(d.quotechar, '"')
+        self.assertTrue(d.doublequote)
 
         mydialect.quotechar = "''"
-        self.assertRaises(csv.Error, mydialect)
+        with self.assertRaises(csv.Error) as cm:
+            mydialect()
+        self.assertEqual(str(cm.exception),
+                         '"quotechar" must be an 1-character string')
 
         mydialect.quotechar = 4
-        self.assertRaises(csv.Error, mydialect)
+        with self.assertRaises(csv.Error) as cm:
+            mydialect()
+        self.assertEqual(str(cm.exception),
+                         '"quotechar" must be string, not int')
 
     def test_delimiter(self):
         class mydialect(csv.Dialect):
@@ -771,12 +781,31 @@
             lineterminator = '\r\n'
             quoting = csv.QUOTE_NONE
         d = mydialect()
+        self.assertEqual(d.delimiter, ";")
 
         mydialect.delimiter = ":::"
-        self.assertRaises(csv.Error, mydialect)
+        with self.assertRaises(csv.Error) as cm:
+            mydialect()
+        self.assertEqual(str(cm.exception),
+                         '"delimiter" must be an 1-character string')
+
+        mydialect.delimiter = ""
+        with self.assertRaises(csv.Error) as cm:
+            mydialect()
+        self.assertEqual(str(cm.exception),
+                         '"delimiter" must be an 1-character string')
+
+        mydialect.delimiter = b","
+        with self.assertRaises(csv.Error) as cm:
+            mydialect()
+        self.assertEqual(str(cm.exception),
+                         '"delimiter" must be string, not bytes')
 
         mydialect.delimiter = 4
-        self.assertRaises(csv.Error, mydialect)
+        with self.assertRaises(csv.Error) as cm:
+            mydialect()
+        self.assertEqual(str(cm.exception),
+                         '"delimiter" must be string, not int')
 
     def test_lineterminator(self):
         class mydialect(csv.Dialect):
@@ -787,12 +816,17 @@
             lineterminator = '\r\n'
             quoting = csv.QUOTE_NONE
         d = mydialect()
+        self.assertEqual(d.lineterminator, '\r\n')
 
         mydialect.lineterminator = ":::"
         d = mydialect()
+        self.assertEqual(d.lineterminator, ":::")
 
         mydialect.lineterminator = 4
-        self.assertRaises(csv.Error, mydialect)
+        with self.assertRaises(csv.Error) as cm:
+            mydialect()
+        self.assertEqual(str(cm.exception),
+                         '"lineterminator" must be a string')
 
 
 class TestSniffer(unittest.TestCase):