Issue #21939: Test IDLE percolator. Original patch by Saimadhav Heblikar.

Lib/idlelib/Percolator.py

 from idlelib.WidgetRedirector import WidgetRedirector
 from idlelib.Delegator import Delegator
 
+
 class Percolator:
 
     def __init__(self, text):
@@ -16,8 +17,10 @@ class Percolator:
         while self.top is not self.bottom:
             self.removefilter(self.top)
         self.top = None
-        self.bottom.setdelegate(None); self.bottom = None
-        self.redir.close(); self.redir = None
+        self.bottom.setdelegate(None)
+        self.bottom = None
+        self.redir.close()
+        self.redir = None
         self.text = None
 
     def insert(self, index, chars, tags=None):
@@ -51,54 +54,52 @@ class Percolator:
             f.setdelegate(filter.delegate)
             filter.setdelegate(None)
 
-def _percolator(parent):
+
+def _percolator(parent):  # htest #
     import tkinter as tk
     import re
+
     class Tracer(Delegator):
         def __init__(self, name):
             self.name = name
             Delegator.__init__(self, None)
+
         def insert(self, *args):
             print(self.name, ": insert", args)
             self.delegate.insert(*args)
+
         def delete(self, *args):
             print(self.name, ": delete", args)
             self.delegate.delete(*args)
-    root = tk.Tk()
-    root.title("Test Percolator")
+
+    box = tk.Toplevel(parent)
+    box.title("Test Percolator")
     width, height, x, y = list(map(int, re.split('[x+]', parent.geometry())))
-    root.geometry("+%d+%d"%(x, y + 150))
-    text = tk.Text(root)
+    box.geometry("+%d+%d" % (x, y + 150))
+    text = tk.Text(box)
     p = Percolator(text)
+    pin = p.insertfilter
+    pout = p.removefilter
     t1 = Tracer("t1")
     t2 = Tracer("t2")
 
     def toggle1():
-        if var1.get() == 0:
-            var1.set(1)
-            p.insertfilter(t1)
-        elif var1.get() == 1:
-            var1.set(0)
-            p.removefilter(t1)
-
+        (pin if var1.get() else pout)(t1)
     def toggle2():
-        if var2.get() == 0:
-            var2.set(1)
-            p.insertfilter(t2)
-        elif var2.get() == 1:
-            var2.set(0)
-            p.removefilter(t2)
+        (pin if var2.get() else pout)(t2)
 
     text.pack()
     var1 = tk.IntVar()
-    cb1 = tk.Checkbutton(root, text="Tracer1", command=toggle1, variable=var1)
+    cb1 = tk.Checkbutton(box, text="Tracer1", command=toggle1, variable=var1)
     cb1.pack()
     var2 = tk.IntVar()
-    cb2 = tk.Checkbutton(root, text="Tracer2", command=toggle2, variable=var2)
+    cb2 = tk.Checkbutton(box, text="Tracer2", command=toggle2, variable=var2)
     cb2.pack()
 
-    root.mainloop()
-
 if __name__ == "__main__":
+    import unittest
+    unittest.main('idlelib.idle_test.test_percolator', verbosity=2,
+                  exit=False)
+
     from idlelib.idle_test.htest import run
     run(_percolator)

Lib/idlelib/idle_test/test_parenmatch.py

 """Test idlelib.ParenMatch."""
 # This must currently be a gui test because ParenMatch methods use
 # several text methods not defined on idlelib.idle_test.mock_tk.Text.
+from test.support import requires
+requires('gui')
 
 import unittest
 from unittest.mock import Mock
-from test.support import requires
 from tkinter import Tk, Text
 from idlelib.ParenMatch import ParenMatch
 
@@ -20,7 +21,6 @@ class ParenMatchTest(unittest.TestCase):
 
     @classmethod
     def setUpClass(cls):
-        requires('gui')
         cls.root = Tk()
         cls.text = Text(cls.root)
         cls.editwin = DummyEditwin(cls.text)

Lib/idlelib/idle_test/test_percolator.py

+'''Test Percolator'''
+from test.support import requires
+requires('gui')
+
+import unittest
+from tkinter import Text, Tk, END
+from idlelib.Percolator import Percolator, Delegator
+
+
+class MyFilter(Delegator):
+    def __init__(self):
+        Delegator.__init__(self, None)
+
+    def insert(self, *args):
+        self.insert_called_with = args
+        self.delegate.insert(*args)
+
+    def delete(self, *args):
+        self.delete_called_with = args
+        self.delegate.delete(*args)
+
+    def uppercase_insert(self, index, chars, tags=None):
+        chars = chars.upper()
+        self.delegate.insert(index, chars)
+
+    def lowercase_insert(self, index, chars, tags=None):
+        chars = chars.lower()
+        self.delegate.insert(index, chars)
+
+    def dont_insert(self, index, chars, tags=None):
+        pass
+
+
+class PercolatorTest(unittest.TestCase):
+
+    @classmethod
+    def setUpClass(cls):
+        cls.root = Tk()
+        cls.text = Text(cls.root)
+
+    @classmethod
+    def tearDownClass(cls):
+        cls.text.destroy()
+        cls.root.destroy()
+        del cls.text, cls.root
+
+    def setUp(self):
+        self.percolator = Percolator(self.text)
+        self.filter_one = MyFilter()
+        self.filter_two = MyFilter()
+        self.percolator.insertfilter(self.filter_one)
+        self.percolator.insertfilter(self.filter_two)
+
+    def tearDown(self):
+        self.percolator.close()
+        self.text.delete('1.0', END)
+
+    def test_insertfilter(self):
+        self.assertIsNotNone(self.filter_one.delegate)
+        self.assertEqual(self.percolator.top, self.filter_two)
+        self.assertEqual(self.filter_two.delegate, self.filter_one)
+        self.assertEqual(self.filter_one.delegate, self.percolator.bottom)
+
+    def test_removefilter(self):
+        filter_three = MyFilter()
+        self.percolator.removefilter(self.filter_two)
+        self.assertEqual(self.percolator.top, self.filter_one)
+        self.assertIsNone(self.filter_two.delegate)
+
+        filter_three = MyFilter()
+        self.percolator.insertfilter(self.filter_two)
+        self.percolator.insertfilter(filter_three)
+        self.percolator.removefilter(self.filter_one)
+        self.assertEqual(self.percolator.top, filter_three)
+        self.assertEqual(filter_three.delegate, self.filter_two)
+        self.assertEqual(self.filter_two.delegate, self.percolator.bottom)
+        self.assertIsNone(self.filter_one.delegate)
+
+    def test_insert(self):
+        self.text.insert('insert', 'foo')
+        self.assertEqual(self.text.get('1.0', END), 'foo\n')
+        self.assertTupleEqual(self.filter_one.insert_called_with,
+                              ('insert', 'foo', None))
+
+    def test_modify_insert(self):
+        self.filter_one.insert = self.filter_one.uppercase_insert
+        self.text.insert('insert', 'bAr')
+        self.assertEqual(self.text.get('1.0', END), 'BAR\n')
+
+    def test_modify_chain_insert(self):
+        filter_three = MyFilter()
+        self.percolator.insertfilter(filter_three)
+        self.filter_two.insert = self.filter_two.uppercase_insert
+        self.filter_one.insert = self.filter_one.lowercase_insert
+        self.text.insert('insert', 'BaR')
+        self.assertEqual(self.text.get('1.0', END), 'bar\n')
+
+    def test_dont_insert(self):
+        self.filter_one.insert = self.filter_one.dont_insert
+        self.text.insert('insert', 'foo bar')
+        self.assertEqual(self.text.get('1.0', END), '\n')
+        self.filter_one.insert = self.filter_one.dont_insert
+        self.text.insert('insert', 'foo bar')
+        self.assertEqual(self.text.get('1.0', END), '\n')
+
+    def test_without_filter(self):
+        self.text.insert('insert', 'hello')
+        self.assertEqual(self.text.get('1.0', 'end'), 'hello\n')
+
+    def test_delete(self):
+        self.text.insert('insert', 'foo')
+        self.text.delete('1.0', '1.2')
+        self.assertEqual(self.text.get('1.0', END), 'o\n')
+        self.assertTupleEqual(self.filter_one.delete_called_with,
+                              ('1.0', '1.2'))
+
+if __name__ == '__main__':
+    unittest.main(verbosity=2)