3 files changed, 90 insertions, 5 deletions

diff --git a/nihil/tests/CMakeLists.txt b/nihil/tests/CMakeLists.txt
index abeab88..25111c2 100644
--- a/nihil/tests/CMakeLists.txt
+++ b/nihil/tests/CMakeLists.txt
@@ -8,10 +8,12 @@ add_executable(nihil.test
 	generic_error.cc
 	getenv.cc
 	guard.cc
+	monad.cc
 	next_word.cc
 	skipws.cc
 	spawn.cc
-	tabulate.cc)
+	tabulate.cc
+)
 
 target_link_libraries(nihil.test PRIVATE
 	nihil
diff --git a/nihil/tests/generic_error.cc b/nihil/tests/generic_error.cc
index b213af9..ee3eccd 100644
--- a/nihil/tests/generic_error.cc
+++ b/nihil/tests/generic_error.cc
@@ -6,12 +6,27 @@
 
 import nihil;
 
-using namespace std::literals;
-
 TEST_CASE("generic_error: basic", "[generic_error]") {
+	using namespace std::literals;
+
+	// C string
+	try {
+		throw nihil::generic_error("test error");
+	} catch (nihil::generic_error const &exc) {
+		REQUIRE(exc.what() == "test error"sv);
+	}
+
+	// std::string
+	try {
+		throw nihil::generic_error("test error"s);
+	} catch (nihil::generic_error const &exc) {
+		REQUIRE(exc.what() == "test error"sv);
+	}
+
+	// std::string_view
 	try {
-		throw nihil::generic_error("{} + {} = {}", 1, 2, 3);
+		throw nihil::generic_error("test error"sv);
 	} catch (nihil::generic_error const &exc) {
-		REQUIRE(exc.what() == "1 + 2 = 3"s);
+		REQUIRE(exc.what() == "test error"sv);
 	}
 }
diff --git a/nihil/tests/monad.cc b/nihil/tests/monad.cc
new file mode 100644
index 0000000..3964494
--- /dev/null
+++ b/nihil/tests/monad.cc
@@ -0,0 +1,68 @@
+/*
+ * This source code is released into the public domain.
+ */
+
+#include <coroutine>
+#include <expected>
+#include <optional>
+
+#include <catch2/catch_test_macros.hpp>
+
+import nihil;
+
+TEST_CASE("monad: co_await std::optional<> with value", "[nihil]")
+{
+	auto get_value = [] -> std::optional<int> {
+		return 42;
+	};
+
+	auto try_get_value = [&get_value] -> std::optional<int> {
+		co_return co_await get_value();
+	};
+
+	auto o = try_get_value();
+	REQUIRE(o == 42);
+}
+
+TEST_CASE("monad: co_await std::optional<> without value", "[nihil]")
+{
+	auto get_value = [] -> std::optional<int> {
+		return {};
+	};
+
+	auto try_get_value = [&get_value] -> std::optional<int> {
+		co_return co_await get_value();
+	};
+
+	auto o = try_get_value();
+	REQUIRE(!o.has_value());
+}
+
+TEST_CASE("monad: co_await std::expected<> with value", "[nihil]")
+{
+	auto get_value = [] -> std::expected<int, std::string> {
+		return 42;
+	};
+
+	auto try_get_value = [&get_value] -> std::expected<int, std::string> {
+		co_return co_await get_value();
+	};
+
+	auto o = try_get_value();
+	REQUIRE(o == 42);
+}
+
+TEST_CASE("monad: co_await std::expected<> with error", "[nihil]")
+{
+	auto get_value = [] -> std::expected<int, std::string> {
+		return std::unexpected("error");
+	};
+
+	auto try_get_value = [&get_value] -> std::expected<int, std::string> {
+		co_return co_await get_value();
+	};
+
+	auto o = try_get_value();
+	REQUIRE(!o);
+	REQUIRE(o.error() == "error");
+}