From ee4483bfbb1746727e44c323a4ac540b482d770d Mon Sep 17 00:00:00 2001
From: light7734 <light7734@tuta.io>
Date: Tue, 15 Jul 2025 15:11:03 +0330
Subject: [PATCH] tests: add tests for time module & refactor: time module

---
 modules/app/src/application.cpp     |  3 +-
 modules/time/CMakeLists.txt         |  5 ++++
 modules/time/include/time/timer.hpp | 22 ++++++---------
 modules/time/src/timer.cpp          | 12 +++++++-
 modules/time/src/timer.tests.cpp    | 44 +++++++++++++++++++++++++++++
 5 files changed, 70 insertions(+), 16 deletions(-)
 create mode 100644 modules/time/src/timer.tests.cpp

diff --git a/modules/app/src/application.cpp b/modules/app/src/application.cpp
index 514da8a..1138743 100644
--- a/modules/app/src/application.cpp
+++ b/modules/app/src/application.cpp
@@ -103,7 +103,8 @@ void Application::update_layers()
 {
 	for (auto &it : *m_layer_stack)
 	{
-		it->on_update(m_timer.get_elapsed_time());
+		// narrowing double -> float
+		it->on_update(static_cast<float>(m_timer.elapsed_time().count()));
 	}
 
 	// TODO(Light): each layer should have their own "delta time"
diff --git a/modules/time/CMakeLists.txt b/modules/time/CMakeLists.txt
index 2f77dbd..74d3bec 100644
--- a/modules/time/CMakeLists.txt
+++ b/modules/time/CMakeLists.txt
@@ -1 +1,6 @@
 add_library_module(time timer.cpp)
+
+add_executable(timer_tests ${CMAKE_CURRENT_SOURCE_DIR}/src/timer.tests.cpp)
+target_include_directories(timer_tests PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include)
+target_link_libraries(timer_tests PRIVATE time test)
+
diff --git a/modules/time/include/time/timer.hpp b/modules/time/include/time/timer.hpp
index 54a603b..a6101de 100644
--- a/modules/time/include/time/timer.hpp
+++ b/modules/time/include/time/timer.hpp
@@ -4,28 +4,22 @@
 
 namespace lt {
 
+/** Simple timer class to keep track of the elapsed time */
 class Timer
 {
 public:
-	Timer();
+	using Timepoint = std::chrono::time_point<std::chrono::steady_clock>;
+	using Duration = std::chrono::duration<double>;
+	using Clock = std::chrono::steady_clock;
 
-	[[nodiscard]] auto get_elapsed_time() const -> float
-	{
-		using std::chrono::duration_cast;
-		using std::chrono::milliseconds;
-		using std::chrono::steady_clock;
+	Timer(Timepoint start = Clock::now());
 
-		auto rep = duration_cast<milliseconds>(steady_clock::now() - m_start).count();
-		return static_cast<float>(rep) / 1000.f;
-	}
+	void reset(Timepoint start = Clock::now());
 
-	void reset()
-	{
-		m_start = std::chrono::steady_clock::now();
-	}
+	[[nodiscard]] auto elapsed_time() const -> Duration;
 
 private:
-	std::chrono::time_point<std::chrono::steady_clock> m_start;
+	Timepoint m_start;
 };
 
 } // namespace lt
diff --git a/modules/time/src/timer.cpp b/modules/time/src/timer.cpp
index 2ce05bc..16bcd86 100644
--- a/modules/time/src/timer.cpp
+++ b/modules/time/src/timer.cpp
@@ -2,8 +2,18 @@
 
 namespace lt {
 
-Timer::Timer(): m_start(std::chrono::steady_clock::now())
+Timer::Timer(Timepoint start): m_start(start)
 {
 }
 
+void Timer::reset(Timepoint start)
+{
+	m_start = start;
+}
+
+[[nodiscard]] auto Timer::elapsed_time() const -> Duration
+{
+	return { std::chrono::steady_clock::now() - m_start };
+}
+
 } // namespace lt
diff --git a/modules/time/src/timer.tests.cpp b/modules/time/src/timer.tests.cpp
new file mode 100644
index 0000000..0f960be
--- /dev/null
+++ b/modules/time/src/timer.tests.cpp
@@ -0,0 +1,44 @@
+#include <ranges>
+#include <test/test.hpp>
+#include <time/timer.hpp>
+
+namespace lt {
+
+using lt::test::expect_le;
+
+lt::test::Suite raii = [] {
+	lt::test::Case { "default" } = [] {
+		auto timer = Timer {};
+	};
+
+	lt::test::Case { "plenty" } = [] {
+		for (auto i : std::views::iota(0, 101))
+		{
+			auto timer = Timer {};
+		}
+	};
+
+	lt::test::Case { "unhappy" } = [] {
+	};
+
+	lt::test::Case { "has sane elapsed time" } = [] {
+		auto elapsed_time = Timer {}.elapsed_time();
+		expect_le(elapsed_time, std::chrono::seconds { 1 });
+	};
+};
+
+lt::test::Suite reset = [] {
+	lt::test::Case { "non-throwing" } = [] {
+		auto timer = Timer {};
+		timer.reset();
+	};
+
+	lt::test::Case { "resets elapsed time" } = [] {
+		auto timer = Timer {};
+		auto elapsed_time = timer.elapsed_time();
+
+		timer.reset();
+	};
+};
+
+} // namespace lt