[base] Add Decrement and assignment operators to AtomicNumber

test/unittests/base/atomic-utils-unittest.cc

Index: test/unittests/base/atomic-utils-unittest.cc
diff --git a/test/unittests/base/atomic-utils-unittest.cc b/test/unittests/base/atomic-utils-unittest.cc
index 06079fe287148a8f87e4a87229da3b23a63e7126..8e90c423e2cd5526352471816078f5e9ac351975 100644
--- a/test/unittests/base/atomic-utils-unittest.cc
+++ b/test/unittests/base/atomic-utils-unittest.cc
@@ -58,6 +58,29 @@ TEST(AtomicNumber, Increment) {
   EXPECT_EQ(std::numeric_limits<size_t>::max(), c.Value());
 }
 
+TEST(AtomicNumber, Decrement) {
+  AtomicNumber<size_t> a(std::numeric_limits<size_t>::max());
+  a.Increment(1);
+  EXPECT_EQ(0, a.Value());
+  a.Decrement(1);
+  EXPECT_EQ(std::numeric_limits<size_t>::max(), a.Value());
+}
+
+TEST(AtomicNumber, OperatorAdditionAssignment) {
+  AtomicNumber<size_t> a(0u);
+  AtomicNumber<size_t> b(std::numeric_limits<size_t>::max());
+  a += b.Value();
+  EXPECT_EQ(a.Value(), b.Value());
+  EXPECT_EQ(b.Value(), std::numeric_limits<size_t>::max());
+}
+
+TEST(AtomicNumber, OperatorSubtractionAssignment) {
+  AtomicNumber<size_t> a(std::numeric_limits<size_t>::max());
+  AtomicNumber<size_t> b(std::numeric_limits<size_t>::max());
+  a -= b.Value();
+  EXPECT_EQ(a.Value(), 0u);
+  EXPECT_EQ(b.Value(), std::numeric_limits<size_t>::max());
+}
 
 namespace {