Add tests demonstrating base 10 fixedness.

test/cast_test.cxx

@@ -19,6 +19,18 @@ TEST(CastIntegerTest, CastsWithBase10) {
   EXPECT_THAT(value, 10);
 }
 
+TEST(CastIntegerTest, DoesNotCastBase8) {
+  auto [value, success] = cast<int>("010");
+  EXPECT_TRUE(success);
+  EXPECT_THAT(value, 10);
+}
+
+TEST(CastIntegerTest, DoesNotCastHex) {
+  auto [value, success] = cast<int>("0x10");
+  EXPECT_FALSE(success);
+  EXPECT_THAT(value, 0);
+}
+
 TEST(CastIntegerTest, FailsOnBadData) {
   auto [value, success] = cast<int>("x");
   EXPECT_FALSE(success);