Check that table evenly divides 256 when generating random string.

webrtc/base/helpers_unittest.cc

 /*
  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 25 matching lines @@
 
 TEST_F(RandomTest, TestCreateRandomString) {
   std::string random = CreateRandomString(256);
   EXPECT_EQ(256U, random.size());
   std::string random2;
   EXPECT_TRUE(CreateRandomString(256, &random2));
   EXPECT_NE(random, random2);
   EXPECT_EQ(256U, random2.size());
 }
 
+TEST_F(RandomTest, TestCreateRandomStringEvenlyDivideTable) {
+  static std::string kUnbiasedTable("01234567");
+  std::string random;
+  EXPECT_TRUE(CreateRandomString(256, kUnbiasedTable, &random));
+  EXPECT_EQ(256U, random.size());
+
+  static std::string kBiasedTable("0123456789");
+  EXPECT_FALSE(CreateRandomString(256, kBiasedTable, &random));
+  EXPECT_EQ(0U, random.size());
+}
+
 TEST_F(RandomTest, TestCreateRandomUuid) {
   std::string random = CreateRandomUuid();
   EXPECT_EQ(36U, random.size());
 }
 
 TEST_F(RandomTest, TestCreateRandomForTest) {
   // Make sure we get the output we expect.
   SetRandomTestMode(true);
   EXPECT_EQ(2154761789U, CreateRandomId());
   EXPECT_EQ("h0ISP4S5SJKH/9EY", CreateRandomString(16));
   EXPECT_EQ("41706e92-cdd3-46d9-a22d-8ff1737ffb11", CreateRandomUuid());
 
   // Reset and make sure we get the same output.
   SetRandomTestMode(true);
   EXPECT_EQ(2154761789U, CreateRandomId());
   EXPECT_EQ("h0ISP4S5SJKH/9EY", CreateRandomString(16));
   EXPECT_EQ("41706e92-cdd3-46d9-a22d-8ff1737ffb11", CreateRandomUuid());
 
   // Test different character sets.
   SetRandomTestMode(true);
   std::string str;
   EXPECT_TRUE(CreateRandomString(16, "a", &str));
   EXPECT_EQ("aaaaaaaaaaaaaaaa", str);
-  EXPECT_TRUE(CreateRandomString(16, "abc", &str));
-  EXPECT_EQ("acbccaaaabbaacbb", str);
+  EXPECT_TRUE(CreateRandomString(16, "abcd", &str));
+  EXPECT_EQ("dbaaabdaccbcabbd", str);
 
   // Turn off test mode for other tests.
   SetRandomTestMode(false);
 }
 
 }  // namespace rtc