Add unique_text_generator

This provides a way to make it easier to test with
unicode text strings. The value returned will be like
TestCase.getUniqueString but the value is six.text_type
and contains unicode.

Change-Id: I3f144e1294a801b23793f7a2520465e15f3a5222

NEWS

@@ -21,6 +21,10 @@ Improvements
   report the lack of result as a test error. This ought to make weird
   concurrency interaction bugs easier to understand. (Jonathan Lange)
 
+* Introduce the unique_text_generator generator function. Similar to the
+  getUniqueString() method, except it creates unique unicode text strings.
+  (Brant Knudson)
+
 * Previously, when gathering details caused by a setUp() failure,
   a traceback occurred if the fixture used the newer _setUp().
   This had the side effect of not clearing up fixtures nor gathering details

doc/for-test-authors.rst

@@ -1357,6 +1357,10 @@ details of certain variables don't actually matter.
 See pages 419-423 of `xUnit Test Patterns`_ by Gerard Meszaros for a detailed
 discussion of creation methods.
 
+``testcase.generate_unique_text()`` is similar to ``getUniqueString``, except
+it generates text that contains unicode characters. The value will be a
+``unicode`` object in Python 2 and a ``str`` object in Python 3.
+
 Test attributes
 ---------------
 

requirements.txt

@@ -7,3 +7,4 @@ pyrsistent
 python-mimeparse
 unittest2>=1.0.0
 traceback2
+six>=1.4.0

testtools/__init__.py

@@ -42,6 +42,7 @@
     'TimestampingStreamResult',
     'try_import',
     'try_imports',
+    'unique_text_generator',
     ]
 
 # Compat - removal announced in 0.9.25.
@@ -77,6 +78,7 @@
         skip,
         skipIf,
         skipUnless,
+        unique_text_generator,
         )
     from testtools.testresult import (
         CopyStreamResult,

testtools/testcase.py

@@ -13,6 +13,7 @@
     'skipIf',
     'skipUnless',
     'TestCase',
+    'unique_text_generator',
     ]
 
 import copy
@@ -29,6 +30,7 @@
 fixtures = try_import('fixtures')
 # To let setup.py work, make this a conditional import.
 unittest = try_imports(['unittest2', 'unittest'])
+import six
 
 from testtools import (
     content,
@@ -182,6 +184,44 @@ def gather_details(source_dict, target_dict):
         target_dict[name] = _copy_content(content_object)
 
 
+def _mods(i, mod):
+    (q, r) = divmod(i, mod)
+    while True:
+        yield r
+        if not q:
+            break
+        (q, r) = divmod(q, mod)
+
+
+def _unique_text(base_cp, cp_range, index):
+    s = six.text_type('')
+    for m in _mods(index, cp_range):
+        s += six.unichr(base_cp + m)
+    return s
+
+
+def unique_text_generator(prefix):
+    """Generates unique text values.
+
+    Generates text values that are unique. Use this when you need arbitrary
+    text in your test, or as a helper for custom anonymous factory methods.
+
+    :param prefix: The prefix for text.
+    :return: text that looks like '<prefix>-<text_with_unicode>'.
+    :rtype: six.text_type
+    """
+    # 0x1e00 is the start of a range of glyphs that are easy to see are
+    # unicode since they've got circles and dots and other diacriticals.
+    # 0x1eff is the end of the range of these diacritical chars.
+    BASE_CP = 0x1e00
+    CP_RANGE = 0x1f00 - BASE_CP
+    index = 0
+    while True:
+        unique_text = _unique_text(BASE_CP, CP_RANGE, index)
+        yield six.text_type('%s-%s') % (prefix, unique_text)
+        index = index + 1
+
+
 class TestCase(unittest.TestCase):
     """Extensions to the basic TestCase.
 

testtools/tests/test_testcase.py

@@ -7,6 +7,8 @@
 import sys
 import unittest
 
+import six
+
 from testtools import (
     DecorateTestCaseResult,
     ErrorHolder,
@@ -1117,7 +1119,7 @@ def test_passes_unexpectedly(self):
 
 
 class TestUniqueFactories(TestCase):
-    """Tests for getUniqueString and getUniqueInteger."""
+    """Tests for getUniqueString, getUniqueInteger, unique_text_generator."""
 
     run_test_with = FullStackRunTest
 
@@ -1145,6 +1147,51 @@ def test_getUniqueString_prefix(self):
         name_two = self.getUniqueString('bar')
         self.assertThat(name_two, Equals('bar-2'))
 
+    def test_unique_text_generator(self):
+        # unique_text_generator yields the prefix's id followed by unique
+        # unicode string.
+        prefix = self.getUniqueString()
+        unique_text_generator = testcase.unique_text_generator(prefix)
+        first_result = next(unique_text_generator)
+        self.assertEqual(six.text_type('%s-%s') % (prefix, _u('\u1e00')),
+                         first_result)
+        # The next value yielded by unique_text_generator is different.
+        second_result = next(unique_text_generator)
+        self.assertEqual(six.text_type('%s-%s') % (prefix, _u('\u1e01')),
+                         second_result)
+
+    def test_mods(self):
+        # given a number and max, generate a list that's the mods.
+        # The list should contain no numbers >= mod
+        self.assertEqual([0], list(testcase._mods(0, 5)))
+        self.assertEqual([1], list(testcase._mods(1, 5)))
+        self.assertEqual([2], list(testcase._mods(2, 5)))
+        self.assertEqual([3], list(testcase._mods(3, 5)))
+        self.assertEqual([4], list(testcase._mods(4, 5)))
+        self.assertEqual([0, 1], list(testcase._mods(5, 5)))
+        self.assertEqual([1, 1], list(testcase._mods(6, 5)))
+        self.assertEqual([2, 1], list(testcase._mods(7, 5)))
+        self.assertEqual([0, 2], list(testcase._mods(10, 5)))
+        self.assertEqual([0, 0, 1], list(testcase._mods(25, 5)))
+        self.assertEqual([1, 0, 1], list(testcase._mods(26, 5)))
+        self.assertEqual([1], list(testcase._mods(1, 100)))
+        self.assertEqual([0, 1], list(testcase._mods(100, 100)))
+        self.assertEqual([0, 10], list(testcase._mods(1000, 100)))
+
+    def test_unique_text(self):
+        self.assertEqual(
+            u'\u1e00',
+            testcase._unique_text(base_cp=0x1e00, cp_range=5, index=0))
+        self.assertEqual(
+            u'\u1e01',
+            testcase._unique_text(base_cp=0x1e00, cp_range=5, index=1))
+        self.assertEqual(
+            u'\u1e00\u1e01',
+            testcase._unique_text(base_cp=0x1e00, cp_range=5, index=5))
+        self.assertEqual(
+            u'\u1e03\u1e02\u1e01',
+            testcase._unique_text(base_cp=0x1e00, cp_range=5, index=38))
+
 
 class TestCloneTestWithNewId(TestCase):
     """Tests for clone_test_with_new_id."""