define stream insertion for std::byte in tests

Change-Id: I5dca691416482ae27ab31bc176fd5217b8e3fd8f

test_ut/test_ut_example.cpp

@@ -2,13 +2,18 @@
 
 #include <array>
 #include <ranges>
+#include <sstream>
 
 auto main() -> int
 {
+  using ::boost::ut::eq;
   using ::boost::ut::expect;
   using ::boost::ut::range_eq;
   using ::boost::ut::test;
 
+  // all of these tests are intended to fail in order to demonstrate information
+  // printed on test failure
+
   test("test range eq, lhs smaller") = [] {
     constexpr auto data1 = std::array{1, 2, 3};
     constexpr auto data2 = std::views::iota(1, 5);
@@ -29,4 +34,12 @@ auto main() -> int
 
     expect(range_eq(data1, data2));
   };
+
+  test("print bytes") = [] {
+    constexpr auto expected = "01100000";
+
+    const auto actual = (std::stringstream{} << std::byte{0b1110'0000}).str();
+
+    expect(eq(expected, actual));
+  };
 }

ut.hpp

@@ -3,10 +3,37 @@
 #include <include/boost/ut.hpp>
 
 #include <algorithm>
+#include <concepts>
+#include <cstddef>
+#include <cstdint>
 #include <optional>
+#include <ostream>
 #include <ranges>
 #include <type_traits>
 
+auto operator<<(std::ostream& os, std::byte b) -> std::ostream&
+{
+  using U = std::uint8_t;
+
+  const auto value = static_cast<std::uint8_t>(b);
+
+  for (auto mask = U{0x80U}; mask != U{}; mask >>= 1U) {
+    os << static_cast<bool>(value & mask);
+  }
+
+  return os;
+}
+template <
+    class Ostream,
+    class = std::enable_if_t<
+        not std::is_reference_v<Ostream> and
+        std::derived_from<Ostream, std::ostream>>>
+auto operator<<(Ostream&& os, std::byte bp) -> Ostream&&
+{
+  os << bp;
+  return std::move(os);
+}
+
 namespace boost::ut {
 namespace detail {