From 9350f017b1bb3f3647b085e408f89ffd7b85ab9f Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Sun, 28 Apr 2024 15:09:01 -0400
Subject: [PATCH] xo-unit: utest: + bpu test to verify bpu is structurual type

---
 include/xo/unit/basis_unit.hpp |  1 +
 include/xo/unit/bpu.hpp        |  3 ++-
 utest/CMakeLists.txt           |  1 +
 utest/bpu.test.cpp             | 36 ++++++++++++++++++++++++++++++++++
 4 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 utest/bpu.test.cpp

diff --git a/include/xo/unit/basis_unit.hpp b/include/xo/unit/basis_unit.hpp
index 57f440b0..922470a0 100644
--- a/include/xo/unit/basis_unit.hpp
+++ b/include/xo/unit/basis_unit.hpp
@@ -31,6 +31,7 @@ namespace xo {
 
             constexpr basis_unit & operator=(const basis_unit & x) = default;
 
+        public: /* need public members so that a basis_unit instance can be a non-type template parameter (a structural type) */
             /** @brief identifies a native unit, e.g. time (in seconds) **/
             dim native_dim_ = dim::invalid;
             /** @brief this unit defined as multiple scalefactor times native unit **/
diff --git a/include/xo/unit/bpu.hpp b/include/xo/unit/bpu.hpp
index 5256c8ed..d9df57a2 100644
--- a/include/xo/unit/bpu.hpp
+++ b/include/xo/unit/bpu.hpp
@@ -109,7 +109,8 @@ namespace xo {
                                  ratio::ratio<Int2>(power_.num(), power_.den()));
             }
 
-            /** @brief this unit represents native dimension taken to this power **/
+        public: /* need public members so that a basis_unit instance can be a non-type template parameter (a structural type) */
+            /** @brief this unit represents basis dimension (bu) taken to this power **/
             power_ratio_type power_;
         };
 
diff --git a/utest/CMakeLists.txt b/utest/CMakeLists.txt
index 7a9fab45..0fcfa866 100644
--- a/utest/CMakeLists.txt
+++ b/utest/CMakeLists.txt
@@ -4,6 +4,7 @@ set(SELF_EXE utest.unit)
 set(SELF_SRCS
     unit_utest_main.cpp  #mpl_unit.test.cpp
     Quantity.test.cpp
+    bpu.test.cpp
     bu.test.cpp
     unit.test.cpp #quantity.test.cpp
 )
diff --git a/utest/bpu.test.cpp b/utest/bpu.test.cpp
new file mode 100644
index 00000000..0c4265b0
--- /dev/null
+++ b/utest/bpu.test.cpp
@@ -0,0 +1,36 @@
+/* @file bpu.test.cpp */
+
+#include "xo/unit/bpu.hpp"
+//#include "xo/indentlog/scope.hpp"
+#include <catch2/catch.hpp>
+
+namespace xo {
+    namespace qty {
+        using bpu64_type = bpu<std::int64_t>;
+
+        /* compile-time test:
+         * verify we can use a bpu as a non-type template parameter.
+         * Will need this for quantity<Repr, Int, natural_unit<Int>>
+         */
+        template <bpu64_type bpu>
+        constexpr bpu_abbrev_type bpu_mpl_abbrev = bpu.abbrev();
+
+        TEST_CASE("bpu", "[bpu]") {
+            //constexpr bool c_debug_flag = false;
+
+            // can get bits from /dev/random by uncommenting the 2nd line below
+            //uint64_t seed = xxx;
+            //rng::Seed<xoshio256ss> seed;
+
+            //auto rng = xo::rng::xoshiro256ss(seed);
+
+            //scope log(XO_DEBUG2(c_debug_flag, "TEST_CASE.bpu"));
+            //log && log("(A)", xtag("foo", foo));
+
+            static_assert(bpu_mpl_abbrev<bpu64_type::unit_power(bu::gram)> == bpu64_type::unit_power(bu::gram).abbrev());
+            REQUIRE(bpu_mpl_abbrev<bpu64_type::unit_power(bu::gram)> == bpu64_type::unit_power(bu::gram).abbrev());
+        } /*TEST_CASE(bpu)*/
+    } /*namespace qty*/
+} /*namespace xo*/
+
+/* end bpu.test.cpp */