Add unit testing 'framework'

- Replace cnl::_impl::identical with test-local equivalanet
- Remove cnl::_impl::assert_same entirely

Author: John McFarlane

include/cnl/_impl/type_traits/assert_same.h

@@ -52,6 +52,7 @@ if (${GTest_FOUND})
     # workaround for github.com/conan-io/conan-center-index/issues/3222
     set(CNL_GTEST_MAIN_TARGET GTest::Main CACHE STRING "alternative GTest target name")
 
+    add_subdirectory(framework)
     add_subdirectory(unit)
 else ()
     message(STATUS "Google Test is required to build unit tests.")

include/cnl/_impl/type_traits/identical.h

@@ -0,0 +1,5 @@
+# test framework
+
+add_library(cnl_test INTERFACE)
+target_include_directories(cnl_test INTERFACE "${CMAKE_CURRENT_LIST_DIR}")
+target_link_libraries(cnl_test INTERFACE ${CNL_GTEST_MAIN_TARGET})

test/CMakeLists.txt

@@ -0,0 +1,25 @@
+
+//          Copyright John McFarlane 2022.
+// Distributed under the Boost Software License, Version 1.0.
+//    (See accompanying file ../LICENSE_1_0.txt or copy at
+//          http://www.boost.org/LICENSE_1_0.txt)
+
+/// \file
+/// \brief definitions of use in tests
+
+#if !defined(CNL_TEST_FRAMEWORK_TEST_H)
+#define CNL_TEST_FRAMEWORK_TEST_H
+
+#include <gtest/gtest.h>
+
+#include <type_traits>
+
+// cnl::_impl::identical - compiles iff same type; returns true iff equal
+template<class A, class B>
+[[nodiscard]] constexpr auto identical(A const& a, B const& b)
+{
+    static_assert(std::is_same<A, B>::value, "different types");
+    return a == b;
+}
+
+#endif  // CNL_TEST_FRAMEWORK_TEST_H

test/framework/CMakeLists.txt

@@ -138,13 +138,6 @@ set(sample_sources
 
 find_package(Boost 1.71.0)
 
-######################################################################
-# add_gtest_dependency
-
-function(add_gtest_dependency target)
-    target_link_libraries("${target}" ${CNL_GTEST_MAIN_TARGET})
-endfunction(add_gtest_dependency)
-
 ######################################################################
 # add test-unit target
 
@@ -155,9 +148,8 @@ add_dependencies(test-all test-unit)
 # test plain - the all.cpp project with *no* tests of compiler flags
 
 add_executable(test-unit-plain all.cpp)
-target_link_libraries(test-unit-plain Cnl)
+target_link_libraries(test-unit-plain Cnl cnl_test)
 add_test(test-unit-plain "${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/test-unit-plain")
-add_gtest_dependency(test-unit-plain)
 add_dependencies(test-unit test-unit-plain)
 
 ######################################################################
@@ -175,12 +167,9 @@ function(make_test source compile_flags)
     add_executable("${target}" "${source}")
     target_include_directories("${target}" PRIVATE "${CMAKE_CURRENT_LIST_DIR}")
     set_target_properties("${target}" PROPERTIES COMPILE_FLAGS "${compile_flags}")
-    target_link_libraries("${target}" Cnl)
+    target_link_libraries("${target}" Cnl cnl_test)
     add_test("${target}" "${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/${target}")
 
-    # Google Test dependency
-    add_gtest_dependency("${target}")
-
     # Boost dependency
     if(Boost_FOUND)
         target_compile_definitions("${target}" PRIVATE "-DCNL_BOOST_ENABLED")

test/framework/test.h

@@ -6,15 +6,11 @@
 
 #include <cnl/_impl/charconv/to_chars.h>
 
-#include <cnl/_impl/type_traits/identical.h>
-
-#include <gtest/gtest.h>
+#include <test.h>
 
 #include <cstdint>
 #include <limits>
 
-using cnl::_impl::identical;
-
 #if !defined(_MSC_VER)
 namespace {
     static_assert(identical(

test/unit/CMakeLists.txt

@@ -9,10 +9,8 @@
 
 #include <cnl/_impl/cmath/abs.h>
 
-#include <cnl/_impl/type_traits/identical.h>
 #include <cnl/cstdint.h>
-
-using cnl::_impl::identical;
+#include <test.h>
 
 namespace test_abs {
     static_assert(identical(cnl::_impl::abs(-302398479), 302398479));

test/unit/_impl/charconv/to_chars.cpp

@@ -6,9 +6,7 @@
 
 #include <cnl/_impl/cmath/sqrt.h>
 
-#include <cnl/_impl/type_traits/identical.h>
-
-using cnl::_impl::identical;
+#include <test.h>
 
 static_assert(identical(0xffffffffLLU, cnl::sqrt(0xfffffffe00000001LLU)));
 static_assert(identical(0xfffffffeLLU, cnl::sqrt(0xfffffffe00000000LLU)));

test/unit/_impl/cmath/abs.cpp

@@ -13,14 +13,10 @@
 #include <cnl/_impl/duplex_integer/operators.h>
 #include <cnl/cstdint.h>
 
-#include <cnl/_impl/type_traits/identical.h>
-
-#include <gtest/gtest.h>
+#include <test.h>
 
 #include <limits>
 
-using cnl::_impl::identical;
-
 namespace {
     namespace test_ctor {
         static_assert(