test: add minimum cases of serializer

tests/CMakeLists.txt

@@ -22,6 +22,7 @@ set(TOML11_TEST_NAMES
     test_parse_table
     test_result
     test_scanner
+    test_serialize
     test_syntax_boolean
     test_syntax_integer
     test_syntax_floating

tests/test_serialize.cpp

@@ -0,0 +1,148 @@
+#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
+#include "doctest.h"
+
+#include <toml.hpp>
+
+TEST_CASE("testing serialization")
+{
+    using namespace toml::literals::toml_literals;
+
+    const auto spec_example = R"(# This is a TOML document
+
+title = "TOML Example"
+
+[owner]
+name = "Tom Preston-Werner"
+dob = 1979-05-27T07:32:00-08:00
+
+[database]
+enabled = true
+ports = [ 8000, 8001, 8002 ]
+data = [ ["delta", "phi"], [3.14] ]
+temp_targets = { cpu = 79.5, case = 72.0 }
+
+[servers]
+
+[servers.alpha]
+ip = "10.0.0.1"
+role = "frontend"
+
+[servers.beta]
+ip = "10.0.0.2"
+role = "backend")"_toml;
+
+    // format and parse
+    const auto v = toml::parse_str(toml::format(spec_example));
+
+    CHECK_EQ(v, spec_example);
+}
+
+TEST_CASE("testing serialization with complicated keys")
+{
+    using namespace toml::literals::toml_literals;
+
+    const auto spec_example = R"(
+[keys]
+
+key = "value"
+bare_key = "value"
+bare-key = "value"
+1234 = "value"
+
+"127.0.0.1"          = "value"
+"character encoding" = "value"
+"ʎǝʞ"                = "value"
+'key2'               = "value"
+'quoted "value"'     = "value"
+
+"" = "blank"
+
+fruits.apple.skin = "thin"
+fruits.apple.color = "red"
+
+fruits.orange.skin = "thick"
+fruits.orange.color = "orange"
+
+site."google.com" = true
+3.14159 = "pi"
+)"_toml;
+
+    // format and parse
+    const auto v = toml::parse_str(toml::format(spec_example));
+
+    CHECK_EQ(v, spec_example);
+}
+
+TEST_CASE("testing serialization with array of tables")
+{
+    using namespace toml::literals::toml_literals;
+
+    const auto spec_example = R"(
+points = [ { x = 1, y = 2, z = 3 },
+           { x = 7, y = 8, z = 9 },
+           { x = 2, y = 4, z = 8 } ]
+
+[[products]]
+name = "Hammer"
+sku = 738594937
+
+[[products]]  # empty table within the array
+
+[[products]]
+name = "Nail"
+sku = 284758393
+
+color = "gray"
+
+[[fruits]]
+name = "apple"
+
+[fruits.physical]  # subtable
+color = "red"
+shape = "round"
+
+[[fruits.varieties]]  # nested array of tables
+name = "red delicious"
+
+[[fruits.varieties]]
+name = "granny smith"
+
+[[fruits]]
+name = "banana"
+
+[[fruits.varieties]]
+name = "plantain"
+)"_toml;
+
+    // format and parse
+    const auto v = toml::parse_str(toml::format(spec_example));
+
+    CHECK_EQ(v, spec_example);
+}
+
+TEST_CASE("testing serialization with locale")
+{
+    std::string current_locale = std::setlocale(LC_ALL, nullptr);
+
+    // fr_FR is a one of locales that uses `,` as a decimal separator.
+    if(const char* try_hyphen = std::setlocale(LC_ALL, "fr_FR.UTF-8"))
+    {
+        current_locale = std::string(try_hyphen);
+    }
+    else if(const char* try_nohyphen = std::setlocale(LC_ALL, "fr_FR.utf8"))
+    {
+        current_locale = std::string(try_nohyphen);
+    }
+
+    MESSAGE("current_locale = ", current_locale);
+
+    const auto v1 = toml::parse_str(R"(
+        pi        = 3.1415_9265
+        large_int = 123_456_789
+    )");
+    const auto v2 = toml::parse_str(toml::format(v1));
+
+    // actually, it checkl if v1 is serialized correctly under FR locale
+    // where 3.1415 -> 3,1415
+    CHECK_EQ(v1, v2);
+}