Add C++ implementation

cpp/tests/test_statement.cpp

@@ -0,0 +1,43 @@
+#include "statement.h"
+
+#include "json.hpp"
+#include "doctest.h"
+#include "ApprovalTests.hpp"
+
+#include <iostream>
+
+namespace
+{
+    std::string get_adjacent_file(const std::string& filename)
+    {
+        return ApprovalTestNamer().getDirectory() + filename;
+    }
+
+    nlohmann::json read_json_file(const std::string& filename)
+    {
+        std::ifstream invoice_stream(filename);
+        if ( ! invoice_stream.is_open())
+        {
+            std::cout << "Error opening file:" << filename << '\n';
+            std::cout << "Error: " << strerror(errno) << '\n';
+        }
+        nlohmann::json result;
+        invoice_stream >> result;
+        return result;
+    }
+}
+
+TEST_CASE("test_example_statement")
+{
+    auto invoice = read_json_file(get_adjacent_file("invoice.json"));
+    auto plays = read_json_file(get_adjacent_file("plays.json"));
+
+    Approvals::verify(statement(invoice, plays));
+}
+
+TEST_CASE("test_statement_with_new_play_types")
+{
+    auto invoice = read_json_file(get_adjacent_file("invoice_new_plays.json"));
+    auto plays = read_json_file(get_adjacent_file("new_plays.json"));
+    CHECK_THROWS_AS(statement(invoice, plays), std::domain_error);
+}