nihil.ucl: improve tests

12 files changed, 436 insertions, 44 deletions

diff --git a/nihil.ucl/boolean.ccm b/nihil.ucl/boolean.ccm
index 8510152..6a93867 100644
--- a/nihil.ucl/boolean.ccm
+++ b/nihil.ucl/boolean.ccm
@@ -18,7 +18,7 @@ import :object;
 namespace nihil::ucl {
 
 export struct boolean final : object {
-	using value_type = bool;
+	using contained_type = bool;
 
 	inline static constexpr object_type ucl_type = object_type::boolean;
 
@@ -41,7 +41,7 @@ export struct boolean final : object {
 	boolean() : boolean(false) {}
 
 	// Create a new boolean from a value.
-	explicit boolean(value_type value)
+	explicit boolean(contained_type value)
 		: object(noref, ::ucl_object_frombool(value))
 	{
 		if (_object == nullptr)
@@ -49,9 +49,9 @@ export struct boolean final : object {
 	}
 
 	// Return this object's value.
-	auto value(this boolean const &self) -> value_type
+	auto value(this boolean const &self) -> contained_type
 	{
-		auto v = value_type{};
+		auto v = contained_type{};
 		auto const *uobj = self.get_ucl_object();
 
 		if (::ucl_object_toboolean_safe(uobj, &v))
@@ -77,13 +77,13 @@ export auto operator<=> (boolean const &a, boolean const &b)
 	return a.value() <=> b.value();
 }
 
-export auto operator== (boolean const &a, boolean::value_type b)
+export auto operator== (boolean const &a, boolean::contained_type b)
 	-> bool
 {
 	return a.value() == b;
 }
 
-export auto operator<=> (boolean const &a, boolean::value_type b)
+export auto operator<=> (boolean const &a, boolean::contained_type b)
 	-> std::strong_ordering
 {
 	return a.value() <=> b;
diff --git a/nihil.ucl/integer.ccm b/nihil.ucl/integer.ccm
index b58c04d..482a716 100644
--- a/nihil.ucl/integer.ccm
+++ b/nihil.ucl/integer.ccm
@@ -18,8 +18,7 @@ import :object;
 namespace nihil::ucl {
 
 export struct integer final : object {
-	using value_type = std::int64_t;
-
+	using contained_type = std::int64_t;
 	inline static constexpr object_type ucl_type = object_type::integer;
 
 	// Create a new integer from a UCL object.
@@ -43,7 +42,7 @@ export struct integer final : object {
 	{}
 
 	// Create a new integer from a value.
-	explicit integer(value_type value)
+	explicit integer(contained_type value)
 		: object(noref, ::ucl_object_fromint(value))
 	{
 		if (_object == nullptr)
@@ -51,9 +50,9 @@ export struct integer final : object {
 	}
 
 	// Return the value of this object.
-	auto value(this integer const &self) -> value_type
+	auto value(this integer const &self) -> contained_type
 	{
-		auto v = value_type{};
+		auto v = contained_type{};
 		auto const *uobj = self.get_ucl_object();
 
 		if (::ucl_object_toint_safe(uobj, &v))
@@ -79,13 +78,13 @@ export auto operator<=> (integer const &a, integer const &b)
 	return a.value() <=> b.value();
 }
 
-export auto operator== (integer const &a, integer::value_type b)
+export auto operator== (integer const &a, integer::contained_type b)
 	-> bool
 {
 	return a.value() == b;
 }
 
-export auto operator<=> (integer const &a, integer::value_type b)
+export auto operator<=> (integer const &a, integer::contained_type b)
 	-> std::strong_ordering
 {
 	return a.value() <=> b;
diff --git a/nihil.ucl/map.ccm b/nihil.ucl/map.ccm
index b486787..c140885 100644
--- a/nihil.ucl/map.ccm
+++ b/nihil.ucl/map.ccm
@@ -164,7 +164,7 @@ struct map final : object {
 		 		     value_type>)
 	map(std::from_range_t, Range &&range)
 		 : map(std::ranges::begin(range),
-			 std::ranges::end(range))
+		   std::ranges::end(range))
 	{
 	}
 
diff --git a/nihil.ucl/object.ccm b/nihil.ucl/object.ccm
index 0814125..b220335 100644
--- a/nihil.ucl/object.ccm
+++ b/nihil.ucl/object.ccm
@@ -137,6 +137,11 @@ protected:
 	// The object we're wrapping.
 	::ucl_object_t *_object = nullptr;
 
+	friend auto swap(object &a, object &b) -> void
+	{
+		std::swap(a._object, b._object);
+	}
+
 private:
 
 	friend struct parser;
diff --git a/nihil.ucl/real.ccm b/nihil.ucl/real.ccm
index 51607f2..260e993 100644
--- a/nihil.ucl/real.ccm
+++ b/nihil.ucl/real.ccm
@@ -17,7 +17,7 @@ import :object;
 namespace nihil::ucl {
 
 export struct real final : object {
-	using value_type = double;
+	using contained_type = double;
 
 	inline static constexpr object_type ucl_type = object_type::real;
 
@@ -42,7 +42,7 @@ export struct real final : object {
 	{}
 
 	// Create a new real from a value.
-	explicit real(value_type value)
+	explicit real(contained_type value)
 		: object(noref, ::ucl_object_fromdouble(value))
 	{
 		if (_object == nullptr)
@@ -50,9 +50,9 @@ export struct real final : object {
 	}
 
 	// Return the value of this real.
-	auto value(this real const &self) -> value_type
+	auto value(this real const &self) -> contained_type
 	{
-		auto v = value_type{};
+		auto v = contained_type{};
 		auto const *uobj = self.get_ucl_object();
 
 		if (::ucl_object_todouble_safe(uobj, &v))
@@ -78,13 +78,13 @@ export auto operator<=> (real const &a, real const &b)
 	return a.value() <=> b.value();
 }
 
-export auto operator== (real const &a, real::value_type b)
+export auto operator== (real const &a, real::contained_type b)
 	-> bool
 {
 	return a.value() == b;
 }
 
-export auto operator<=> (real const &a, real::value_type b)
+export auto operator<=> (real const &a, real::contained_type b)
 	-> std::partial_ordering
 {
 	return a.value() <=> b;
diff --git a/nihil.ucl/string.ccm b/nihil.ucl/string.ccm
index 64f88dc..f92c82c 100644
--- a/nihil.ucl/string.ccm
+++ b/nihil.ucl/string.ccm
@@ -17,10 +17,16 @@ import :object;
 namespace nihil::ucl {
 
 export struct string final : object {
-	using value_type = std::string_view;
-
+	using contained_type = std::string_view;
 	inline static constexpr object_type ucl_type = object_type::string;
 
+	using value_type = char const;
+	using size_type = std::size_t;
+	using difference_type = std::ptrdiff_t;
+	using reference = value_type &;
+	using pointer = value_type *;
+	using iterator = pointer;
+
 	// Create a new string from a UCL object.
 	string(ref_t, ::ucl_object_t const *uobj)
 		: object(nihil::ucl::ref, uobj)
@@ -71,7 +77,7 @@ export struct string final : object {
 	{}
 
 	// Return the value of this string.
-	auto value(this string const &self) -> value_type
+	auto value(this string const &self) -> contained_type
 	{
 		char const *dptr{};
 		std::size_t dlen;
@@ -83,6 +89,42 @@ export struct string final : object {
 		// This should never fail.
 		std::abort();
 	}
+
+	// Return the size of this string.
+	auto size(this string const &self) -> size_type
+	{
+		return self.value().size();
+	}
+
+	// Test if this string is empty.
+	auto empty(this string const &self) -> bool
+	{
+		return self.size() == 0;
+	}
+
+	// Access this string's data
+	auto data(this string const &self) -> pointer
+	{
+		char const *dptr{};
+
+		auto const *uobj = self.get_ucl_object();
+		if (::ucl_object_tostring_safe(uobj, &dptr))
+			return dptr;
+
+		// This should never fail.
+		std::abort();
+	}
+
+	// Iterator access
+	auto begin(this string const &self) -> iterator
+	{
+		return self.data();
+	}
+
+	auto end(this string const &self) -> iterator
+	{
+		return self.data() + self.size();
+	}
 };
 
 /*
diff --git a/nihil.ucl/tests/array.cc b/nihil.ucl/tests/array.cc
index 023b3bf..ce0976f 100644
--- a/nihil.ucl/tests/array.cc
+++ b/nihil.ucl/tests/array.cc
@@ -3,14 +3,36 @@
  */
 
 #include <algorithm>
+#include <concepts>
 #include <ranges>
 #include <string>
 
 #include <catch2/catch_test_macros.hpp>
+#include <ucl.h>
 
 import nihil.ucl;
 
-TEST_CASE("ucl: array: construct", "[ucl]")
+TEST_CASE("ucl: array: invariants", "[ucl]")
+{
+	using namespace nihil::ucl;
+
+	REQUIRE(array<>::ucl_type == object_type::array);
+	REQUIRE(static_cast<::ucl_type>(array<>::ucl_type) == UCL_ARRAY);
+
+	static_assert(std::destructible<array<>>);
+	static_assert(std::default_initializable<array<>>);
+	static_assert(std::move_constructible<array<>>);
+	static_assert(std::copy_constructible<array<>>);
+	static_assert(std::equality_comparable<array<>>);
+	static_assert(std::totally_ordered<array<>>);
+	static_assert(std::swappable<array<>>);
+	
+	static_assert(std::ranges::sized_range<array<integer>>);
+	static_assert(std::same_as<std::ranges::range_value_t<array<integer>>,
+				   integer>);
+}
+
+TEST_CASE("ucl: array: default construct", "[ucl]")
 {
 	using namespace nihil::ucl;
 
@@ -19,6 +41,42 @@ TEST_CASE("ucl: array: construct", "[ucl]")
 	REQUIRE(str(arr.type()) == "array");
 }
 
+TEST_CASE("ucl: array: construct from range", "[ucl]")
+{
+	using namespace nihil::ucl;
+
+	auto vec = std::vector{integer(1), integer(42)};
+	auto arr = array<integer>(std::from_range, vec);
+
+	REQUIRE(arr.size() == 2);
+	REQUIRE(arr[0] == 1);
+	REQUIRE(arr[1] == 42);
+}
+
+TEST_CASE("ucl: array: construct from iterator pair", "[ucl]")
+{
+	using namespace nihil::ucl;
+
+	auto vec = std::vector{integer(1), integer(42)};
+	auto arr = array<integer>(std::ranges::begin(vec),
+				  std::ranges::end(vec));
+
+	REQUIRE(arr.size() == 2);
+	REQUIRE(arr[0] == 1);
+	REQUIRE(arr[1] == 42);
+}
+
+TEST_CASE("ucl: array: construct from initializer_list", "[ucl]")
+{
+	using namespace nihil::ucl;
+
+	auto arr = array<integer>{integer(1), integer(42)};
+
+	REQUIRE(arr.size() == 2);
+	REQUIRE(arr[0] == 1);
+	REQUIRE(arr[1] == 42);
+}
+
 TEST_CASE("ucl: array: push_back", "[ucl]")
 {
 	using namespace nihil::ucl;
@@ -45,10 +103,9 @@ TEST_CASE("ucl: array: compare", "[ucl]")
 {
 	using namespace nihil::ucl;
 
-	auto arr = array<integer>();
-	arr.push_back(integer(1));
-	arr.push_back(integer(42));
-	arr.push_back(integer(666));
+	auto arr = array<integer>{
+		integer(1), integer(42), integer(666)
+	};
 
 	auto arr2 = array<integer>();
 	REQUIRE(arr != arr2);
@@ -58,10 +115,10 @@ TEST_CASE("ucl: array: compare", "[ucl]")
 	arr2.push_back(integer(666));
 	REQUIRE(arr == arr2);
 
-	auto arr3 = array<integer>();
-	arr3.push_back(integer(1));
-	arr3.push_back(integer(1));
-	arr3.push_back(integer(1));
+	auto arr3 = array<integer>{
+		integer(1), integer(1), integer(1)
+	};
+
 	REQUIRE(arr != arr3);
 }
 
@@ -124,7 +181,6 @@ TEST_CASE("ucl: array is a sized_range", "[ucl]")
 	using namespace nihil::ucl;
 
 	auto arr = array<integer>{integer(1), integer(42), integer(666)};
-	static_assert(std::ranges::sized_range<decltype(arr)>);
 
 	auto size = std::ranges::size(arr);
 	REQUIRE(size == 3);
@@ -143,7 +199,7 @@ TEST_CASE("ucl: array is a sized_range", "[ucl]")
 
 	auto arr_as_ints =
 		arr | std::views::transform(&integer::value);
-	auto int_vec = std::vector<integer::value_type>();
+	auto int_vec = std::vector<integer::contained_type>();
 	std::ranges::copy(arr_as_ints, std::back_inserter(int_vec));
 	REQUIRE(int_vec == std::vector<std::int64_t>{1, 42, 666});
 
diff --git a/nihil.ucl/tests/boolean.cc b/nihil.ucl/tests/boolean.cc
index ed5e1d7..49dc408 100644
--- a/nihil.ucl/tests/boolean.cc
+++ b/nihil.ucl/tests/boolean.cc
@@ -2,16 +2,29 @@
  * This source code is released into the public domain.
  */
 
+#include <concepts>
 #include <string>
 
 #include <catch2/catch_test_macros.hpp>
+#include <ucl.h>
 
 import nihil.ucl;
 
-TEST_CASE("ucl: boolean: construct", "[ucl]")
+TEST_CASE("ucl: boolean: invariants", "[ucl]")
 {
-	auto b = nihil::ucl::boolean(true);
-	REQUIRE(b == true);
+	using namespace nihil::ucl;
+
+	static_assert(std::same_as<bool, boolean::contained_type>);
+	REQUIRE(boolean::ucl_type == object_type::boolean);
+	REQUIRE(static_cast<::ucl_type>(boolean::ucl_type) == UCL_BOOLEAN);
+
+	static_assert(std::destructible<boolean>);
+	static_assert(std::default_initializable<boolean>);
+	static_assert(std::move_constructible<boolean>);
+	static_assert(std::copy_constructible<boolean>);
+	static_assert(std::equality_comparable<boolean>);
+	static_assert(std::totally_ordered<boolean>);
+	static_assert(std::swappable<boolean>);
 }
 
 TEST_CASE("ucl: boolean: default construct", "[ucl]")
@@ -20,6 +33,42 @@ TEST_CASE("ucl: boolean: default construct", "[ucl]")
 	REQUIRE(b == false);
 }
 
+TEST_CASE("ucl: boolean: construct from value", "[ucl]")
+{
+	auto b = nihil::ucl::boolean(true);
+	REQUIRE(b == true);
+}
+
+TEST_CASE("ucl: boolean: swap", "[ucl]")
+{
+	// do not add using namespace nihil::ucl
+	
+	auto b1 = nihil::ucl::boolean(true);
+	auto b2 = nihil::ucl::boolean(false);
+
+	swap(b1, b2);
+
+	REQUIRE(b1 == false);
+	REQUIRE(b2 == true);
+}
+
+TEST_CASE("ucl: boolean: value()", "[ucl]")
+{
+	auto b = nihil::ucl::boolean(true);
+	REQUIRE(b.value() == true);
+}
+
+TEST_CASE("ucl: boolean: key()", "[ucl]")
+{
+	using namespace nihil::ucl;
+
+	auto obj = parse("a_bool = true");
+	REQUIRE(object_cast<boolean>(obj["a_bool"]).key() == "a_bool");
+
+	auto b = nihil::ucl::boolean(true);
+	REQUIRE(b.key() == "");
+}
+
 TEST_CASE("ucl: boolean: operator==", "[ucl]")
 {
 	auto b = nihil::ucl::boolean(true);
@@ -54,6 +103,13 @@ TEST_CASE("ucl: boolean: parse", "[ucl]")
 
 TEST_CASE("ucl: boolean: emit", "[ucl]")
 {
+	auto b = nihil::ucl::boolean(true);
+	auto str = std::format("{}", b);
+	REQUIRE(str == "true");
+}
+
+TEST_CASE("ucl: boolean: parse and emit", "[ucl]")
+{
 	auto ucl = nihil::ucl::parse("bool = true;");
 
 	auto output = std::string();
diff --git a/nihil.ucl/tests/integer.cc b/nihil.ucl/tests/integer.cc
index ad513ca..811a864 100644
--- a/nihil.ucl/tests/integer.cc
+++ b/nihil.ucl/tests/integer.cc
@@ -2,16 +2,30 @@
  * This source code is released into the public domain.
  */
 
+#include <concepts>
+#include <cstdint>
 #include <string>
 
 #include <catch2/catch_test_macros.hpp>
+#include <ucl.h>
 
 import nihil.ucl;
 
-TEST_CASE("ucl: integer: construct", "[ucl]")
+TEST_CASE("ucl: integer: invariants", "[ucl]")
 {
-	auto i = nihil::ucl::integer(42);
-	REQUIRE(i == 42);
+	using namespace nihil::ucl;
+
+	static_assert(std::same_as<std::int64_t, integer::contained_type>);
+	REQUIRE(integer::ucl_type == object_type::integer);
+	REQUIRE(static_cast<::ucl_type>(integer::ucl_type) == UCL_INT);
+
+	static_assert(std::destructible<integer>);
+	static_assert(std::default_initializable<integer>);
+	static_assert(std::move_constructible<integer>);
+	static_assert(std::copy_constructible<integer>);
+	static_assert(std::equality_comparable<integer>);
+	static_assert(std::totally_ordered<integer>);
+	static_assert(std::swappable<integer>);
 }
 
 TEST_CASE("ucl: integer: default construct", "[ucl]")
@@ -20,6 +34,42 @@ TEST_CASE("ucl: integer: default construct", "[ucl]")
 	REQUIRE(i == 0);
 }
 
+TEST_CASE("ucl: integer: construct", "[ucl]")
+{
+	auto i = nihil::ucl::integer(42);
+	REQUIRE(i == 42);
+}
+
+TEST_CASE("ucl: integer: swap", "[ucl]")
+{
+	// do not add using namespace nihil::ucl
+	
+	auto i1 = nihil::ucl::integer(1);
+	auto i2 = nihil::ucl::integer(2);
+
+	swap(i1, i2);
+
+	REQUIRE(i1 == 2);
+	REQUIRE(i2 == 1);
+}
+
+TEST_CASE("ucl: integer: value()", "[ucl]")
+{
+	auto i = nihil::ucl::integer(42);
+	REQUIRE(i.value() == 42);
+}
+
+TEST_CASE("ucl: integer: key()", "[ucl]")
+{
+	using namespace nihil::ucl;
+
+	auto obj = parse("an_int = 42");
+	REQUIRE(object_cast<integer>(obj["an_int"]).key() == "an_int");
+
+	auto i = nihil::ucl::integer(42);
+	REQUIRE(i.key() == "");
+}
+
 TEST_CASE("ucl: integer: operator==", "[ucl]")
 {
 	auto i = nihil::ucl::integer(42);
@@ -42,7 +92,7 @@ TEST_CASE("ucl: integer: operator<=>", "[ucl]")
 	REQUIRE(i > nihil::ucl::integer(1));
 }
 
-TEST_CASE("ucl: parse: integer", "[ucl]")
+TEST_CASE("ucl: integer: parse", "[ucl]")
 {
 	using namespace std::literals;
 
@@ -54,6 +104,13 @@ TEST_CASE("ucl: parse: integer", "[ucl]")
 
 TEST_CASE("ucl: integer: emit", "[ucl]")
 {
+	auto i = nihil::ucl::integer(42);
+	auto str = std::format("{}", i);
+	REQUIRE(str == "42");
+}
+
+TEST_CASE("ucl: integer: parse and emit", "[ucl]")
+{
 	auto ucl = nihil::ucl::parse("int = 42;");
 
 	auto output = std::string();
diff --git a/nihil.ucl/tests/map.cc b/nihil.ucl/tests/map.cc
index d106c79..5d2fbe1 100644
--- a/nihil.ucl/tests/map.cc
+++ b/nihil.ucl/tests/map.cc
@@ -2,10 +2,33 @@
  * This source code is released into the public domain.
  */
 
+#include <concepts>
+
 #include <catch2/catch_test_macros.hpp>
+#include <ucl.h>
 
 import nihil.ucl;
 
+TEST_CASE("ucl: map: invariants", "[ucl]")
+{
+	using namespace nihil::ucl;
+
+	REQUIRE(map<>::ucl_type == object_type::object);
+	REQUIRE(static_cast<::ucl_type>(map<>::ucl_type) == UCL_OBJECT);
+
+	static_assert(std::destructible<map<>>);
+	static_assert(std::default_initializable<map<>>);
+	static_assert(std::move_constructible<map<>>);
+	static_assert(std::copy_constructible<map<>>);
+	static_assert(std::equality_comparable<map<>>);
+	static_assert(std::totally_ordered<map<>>);
+	static_assert(std::swappable<map<>>);
+
+	static_assert(std::ranges::range<map<integer>>);
+	static_assert(std::same_as<std::pair<std::string_view, integer>,
+				   std::ranges::range_value_t<map<integer>>>);
+}
+
 TEST_CASE("ucl: map: default construct", "[ucl]")
 {
 	auto map = nihil::ucl::map<>();
@@ -27,6 +50,41 @@ TEST_CASE("ucl: map: construct from initializer_list", "[ucl]")
 	REQUIRE(map["42"] == 42);
 }
 
+TEST_CASE("ucl: map: construct from range", "[ucl]")
+{
+	using namespace nihil::ucl;
+	using namespace std::literals;
+
+	auto vec = std::vector<std::pair<std::string_view, integer>>{
+		{"1"sv, integer(1)},
+		{"42"sv, integer(42)},
+	};
+
+	auto map = nihil::ucl::map<integer>(std::from_range, vec);
+
+	REQUIRE(str(map.type()) == "object");
+	REQUIRE(map["1"] == 1);
+	REQUIRE(map["42"] == 42);
+}
+
+TEST_CASE("ucl: map: construct from iterator pair", "[ucl]")
+{
+	using namespace nihil::ucl;
+	using namespace std::literals;
+
+	auto vec = std::vector<std::pair<std::string_view, integer>>{
+		{"1"sv, integer(1)},
+		{"42"sv, integer(42)},
+	};
+
+	auto map = nihil::ucl::map<integer>(std::ranges::begin(vec),
+					    std::ranges::end(vec));
+
+	REQUIRE(str(map.type()) == "object");
+	REQUIRE(map["1"] == 1);
+	REQUIRE(map["42"] == 42);
+}
+
 TEST_CASE("ucl: map: insert", "[ucl]")
 {
 	using namespace nihil::ucl;
diff --git a/nihil.ucl/tests/real.cc b/nihil.ucl/tests/real.cc
index 4bd9b3f..b11c113 100644
--- a/nihil.ucl/tests/real.cc
+++ b/nihil.ucl/tests/real.cc
@@ -2,13 +2,32 @@
  * This source code is released into the public domain.
  */
 
+#include <concepts>
 #include <string>
 
 #include <catch2/catch_test_macros.hpp>
 #include <catch2/matchers/catch_matchers_floating_point.hpp>
+#include <ucl.h>
 
 import nihil.ucl;
 
+TEST_CASE("ucl: real: invariants", "[ucl]")
+{
+	using namespace nihil::ucl;
+
+	static_assert(std::same_as<double, real::contained_type>);
+	REQUIRE(real::ucl_type == object_type::real);
+	REQUIRE(static_cast<::ucl_type>(real::ucl_type) == UCL_FLOAT);
+
+	static_assert(std::destructible<real>);
+	static_assert(std::default_initializable<real>);
+	static_assert(std::move_constructible<real>);
+	static_assert(std::copy_constructible<real>);
+	static_assert(std::equality_comparable<real>);
+	static_assert(std::totally_ordered<real>);
+	static_assert(std::swappable<real>);
+}
+
 TEST_CASE("ucl: real: construct", "[ucl]")
 {
 	auto obj = nihil::ucl::real(42.1);
@@ -22,6 +41,19 @@ TEST_CASE("ucl: real: default construct", "[ucl]")
 	REQUIRE(i == 0);
 }
 
+TEST_CASE("ucl: real: swap", "[ucl]")
+{
+	// do not add using namespace nihil::ucl
+	
+	auto r1 = nihil::ucl::real(1);
+	auto r2 = nihil::ucl::real(2);
+
+	swap(r1, r2);
+
+	REQUIRE(r1 == 2.);
+	REQUIRE(r2 == 1.);
+}
+
 TEST_CASE("ucl: real: operator==", "[ucl]")
 {
 	auto i = nihil::ucl::real(42.5);
diff --git a/nihil.ucl/tests/string.cc b/nihil.ucl/tests/string.cc
index 19052cd..e7eb0ad 100644
--- a/nihil.ucl/tests/string.cc
+++ b/nihil.ucl/tests/string.cc
@@ -2,6 +2,7 @@
  * This source code is released into the public domain.
  */
 
+#include <concepts>
 #include <list>
 #include <string>
 #include <vector>
@@ -15,9 +16,20 @@ TEST_CASE("ucl: string: invariants", "[ucl]")
 {
 	using namespace nihil::ucl;
 
-	static_assert(std::same_as<std::string_view, string::value_type>);
+	static_assert(std::same_as<std::string_view, string::contained_type>);
 	REQUIRE(string::ucl_type == object_type::string);
 	REQUIRE(static_cast<::ucl_type>(string::ucl_type) == UCL_STRING);
+
+	static_assert(std::destructible<string>);
+	static_assert(std::default_initializable<string>);
+	static_assert(std::move_constructible<string>);
+	static_assert(std::copy_constructible<string>);
+	static_assert(std::equality_comparable<string>);
+	static_assert(std::totally_ordered<string>);
+	static_assert(std::swappable<string>);
+
+	static_assert(std::ranges::contiguous_range<string>);
+	static_assert(std::same_as<char, std::ranges::range_value_t<string>>);
 }
 
 TEST_CASE("ucl: string: default construct", "[ucl]")
@@ -74,6 +86,74 @@ TEST_CASE("ucl: string: construct from non-contiguous iterator", "[ucl]")
 	REQUIRE(str == "testing");
 }
 
+TEST_CASE("ucl: string: swap", "[ucl]")
+{
+	// do not add using namespace nihil::ucl
+	
+	auto s1 = nihil::ucl::string("one");
+	auto s2 = nihil::ucl::string("two");
+
+	swap(s1, s2);
+
+	REQUIRE(s1 == "two");
+	REQUIRE(s2 == "one");
+}
+
+TEST_CASE("ucl: string: value()", "[ucl]")
+{
+	auto s = nihil::ucl::string("te\"st");
+	REQUIRE(s.value() == "te\"st");
+}
+
+TEST_CASE("ucl: string: key()", "[ucl]")
+{
+	using namespace nihil::ucl;
+
+	auto obj = parse("a_string = \"test\"");
+	REQUIRE(object_cast<string>(obj["a_string"]).key() == "a_string");
+
+	auto s = nihil::ucl::string("test");
+	REQUIRE(s.key() == "");
+}
+
+TEST_CASE("ucl: string: size", "[ucl]")
+{
+	using namespace nihil::ucl;
+
+	REQUIRE(string().size() == 0);
+	REQUIRE(string("test").size() == 4);
+}
+
+TEST_CASE("ucl: string: empty", "[ucl]")
+{
+	using namespace nihil::ucl;
+
+	REQUIRE(string().empty() == true);
+	REQUIRE(string("test").empty() == false);
+}
+
+TEST_CASE("ucl: string: iterator", "[ucl]")
+{
+	auto str = nihil::ucl::string("test");
+
+	auto begin = std::ranges::begin(str);
+	static_assert(std::contiguous_iterator<decltype(begin)>);
+
+	auto end = std::ranges::end(str);
+	static_assert(std::sentinel_for<decltype(end), decltype(begin)>);
+
+	REQUIRE(*begin == 't');
+	++begin;
+	REQUIRE(*begin == 'e');
+	++begin;
+	REQUIRE(*begin == 's');
+	++begin;
+	REQUIRE(*begin == 't');
+	++begin;
+
+	REQUIRE(begin == end);
+}
+
 TEST_CASE("ucl: string: operator==", "[ucl]")
 {
 	auto str = nihil::ucl::string("testing");
@@ -108,14 +188,21 @@ TEST_CASE("ucl: string: parse", "[ucl]")
 {
 	using namespace std::literals;
 
-	auto obj = nihil::ucl::parse("value = \"str\""sv);
+	auto obj = nihil::ucl::parse("value = \"te\\\"st\""sv);
 	auto v = obj["value"];
 	REQUIRE(v.key() == "value");
-	REQUIRE(object_cast<nihil::ucl::string>(v) == "str");
+	REQUIRE(object_cast<nihil::ucl::string>(v) == "te\"st");
 }
 
 TEST_CASE("ucl: string: emit", "[ucl]")
 {
+	auto s = nihil::ucl::string("te\"st");
+	auto str = std::format("{}", s);
+	REQUIRE(str == "\"te\\\"st\"");
+}
+
+TEST_CASE("ucl: string: parse and emit", "[ucl]")
+{
 	auto ucl = nihil::ucl::parse("str = \"te\\\"st\";");
 
 	auto output = std::string();