commit e12188119330a6508d542684f10ac29323df2d74
author Gilad Arnold <garnold@chromium.org> Wed May 07 12:21:36 2014 -0700
committer chrome-internal-fetch <chrome-internal-fetch@google.com> Fri May 09 00:28:01 2014 +0000
tree c69786cf15ba498fa44e65c5326fa3e66c93299e
parent f967ebeb1851548a37c01db2bc4f78b8db2d2f99

PM: Get a random value between [min, max].

This is required for generating random values used for scattering. In
doing so, we shift to using an STL provided generator and distribution
function.

BUG=chromium:358323
TEST=Unit tests.

Change-Id: I6e758605f1d8123ab73a81906ecf7ad83c5e6cb9
Reviewed-on: https://chromium-review.googlesource.com/198780
Tested-by: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Gilad Arnold <garnold@chromium.org>

policy_manager/prng_unittest.cc

diff --git a/policy_manager/prng_unittest.cc b/policy_manager/prng_unittest.cc
index 4bdf836..cbe7690 100644
--- a/policy_manager/prng_unittest.cc
+++ b/policy_manager/prng_unittest.cc
@@ -17,7 +17,7 @@
   PRNG b(42);
 
   for (int i = 0; i < 1000; ++i) {
-    EXPECT_EQ(a.rand(), b.rand()) << "Iteration i=" << i;
+    EXPECT_EQ(a.Rand(), b.Rand()) << "Iteration i=" << i;
   }
 }
 
@@ -25,12 +25,12 @@
   PRNG a(42);
   PRNG b(5);
 
-  vector<int> values_a;
-  vector<int> values_b;
+  vector<uint32_t> values_a;
+  vector<uint32_t> values_b;
 
   for (int i = 0; i < 100; ++i) {
-    values_a.push_back(a.rand());
-    values_b.push_back(b.rand());
+    values_a.push_back(a.Rand());
+    values_b.push_back(b.Rand());
   }
   EXPECT_NE(values_a, values_b);
 }
@@ -38,10 +38,10 @@
 TEST(PmPRNGTest, IsNotConstant) {
   PRNG prng(5);
 
-  int initial_value = prng.rand();
+  uint32_t initial_value = prng.Rand();
   bool prng_is_constant = true;
   for (int i = 0; i < 100; ++i) {
-    if (prng.rand() != initial_value) {
+    if (prng.Rand() != initial_value) {
       prng_is_constant = false;
       break;
     }
@@ -49,4 +49,19 @@
   EXPECT_FALSE(prng_is_constant) << "After 100 iterations.";
 }
 
+TEST(PmPRNGTest, RandCoversRange) {
+  PRNG a(42);
+  int hits[11] = { 0 };
+
+  for (int i = 0; i < 1000; i++) {
+    int r = a.RandMinMax(0, 10);
+    ASSERT_LE(0, r);
+    ASSERT_GE(10, r);
+    hits[r]++;
+  }
+
+  for (auto& hit : hits)
+    EXPECT_LT(0, hit);
+}
+
 }  // namespace chromeos_policy_manager