Adding test for count_if

src/tools/std20/algorithm/test/CMakeLists.txt

@@ -1,4 +1,5 @@
 add_cpp_test( std20.algorithm.count             count.test.cpp )
+add_cpp_test( std20.algorithm.count_if          count_if.test.cpp )
 add_cpp_test( std20.algorithm.adjacent_find     adjacent_find.test.cpp )
 add_cpp_test( std20.algorithm.equal             equal.test.cpp )
 add_cpp_test( std20.algorithm.find              find.test.cpp )

src/tools/std20/algorithm/test/count_if.test.cpp

@@ -0,0 +1,28 @@
+// include Catch2
+#include <catch2/catch_test_macros.hpp>
+
+// what we are testing
+#include "tools/std20/algorithm.hpp"
+
+// other includes
+
+// convenience typedefs
+using namespace njoy::tools;
+
+SCENARIO( "adjacent_find" ) {
+
+  int a[] = { 1, 2, 3, 3, 4, 5 };
+
+  std::vector< int > va = { 1, 2, 3, 3, 4, 5 };
+
+  auto compare = [] ( auto&& value ) { return value % 2 == 0; };
+
+  CHECK( 2 == std20::count_if( std20::ranges::begin( a ), std20::ranges::end( a ), compare ) );
+
+  CHECK( 2 == std20::count_if( std20::ranges::begin( va ), std20::ranges::end( va ), compare ) );
+
+  CHECK( 2 == std20::count_if( a, compare ) );
+
+  CHECK( 2 == std20::count_if( va, compare ) );
+
+} // SCENARIO