From c7c467230c90693ae11d793e95fb5c22005edb84 Mon Sep 17 00:00:00 2001
From: Marcus Holland-Moritz <github@mhxnet.de>
Date: Thu, 4 Jan 2024 22:05:58 +0100
Subject: [PATCH] test: add speedometer test

---
 CMakeLists.txt               |  1 +
 include/dwarfs/speedometer.h | 24 ++++++----
 test/speedometer_test.cpp    | 90 ++++++++++++++++++++++++++++++++++++
 3 files changed, 106 insertions(+), 9 deletions(-)
 create mode 100644 test/speedometer_test.cpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index b8cae422..69cac3ec 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -608,6 +608,7 @@ if(WITH_TESTS)
     metadata_requirements_test
     pcm_sample_transformer_test
     pcmaudio_categorizer_test
+    speedometer_test
     terminal_test
     tool_main_test
     tools_test
diff --git a/include/dwarfs/speedometer.h b/include/dwarfs/speedometer.h
index b508212d..8a28e10b 100644
--- a/include/dwarfs/speedometer.h
+++ b/include/dwarfs/speedometer.h
@@ -26,14 +26,17 @@
 
 namespace dwarfs {
 
-template <typename T>
-class speedometer {
+template <typename ClockT, typename ValueT>
+class basic_speedometer {
  public:
-  speedometer(std::chrono::milliseconds window_length)
+  using clock_type = ClockT;
+  using value_type = ValueT;
+
+  basic_speedometer(std::chrono::milliseconds window_length)
       : window_length_{window_length} {}
 
-  void put(T s) {
-    auto now = std::chrono::steady_clock::now();
+  void put(value_type s) {
+    auto now = clock_type::now();
     auto old = now - window_length_;
 
     while (!samples_.empty() && samples_.front().first < old) {
@@ -43,9 +46,9 @@ class speedometer {
     samples_.emplace_back(now, s);
   }
 
-  T num_per_second() const {
+  value_type num_per_second() const {
     if (samples_.size() < 2) {
-      return T();
+      return value_type();
     }
     auto const& first = samples_.front();
     auto const& last = samples_.back();
@@ -53,14 +56,17 @@ class speedometer {
     auto const dv = last.second - first.second;
     auto const elapsed_ms =
         std::chrono::duration_cast<std::chrono::milliseconds>(dt).count();
-    return elapsed_ms > 0 ? (1000 * dv) / elapsed_ms : T();
+    return elapsed_ms > 0 ? (1000 * dv) / elapsed_ms : value_type();
   }
 
   void clear() { samples_.clear(); }
 
  private:
-  std::deque<std::pair<std::chrono::steady_clock::time_point, T>> samples_;
+  std::deque<std::pair<typename clock_type::time_point, value_type>> samples_;
   std::chrono::milliseconds window_length_;
 };
 
+template <typename T>
+using speedometer = basic_speedometer<std::chrono::steady_clock, T>;
+
 } // namespace dwarfs
diff --git a/test/speedometer_test.cpp b/test/speedometer_test.cpp
new file mode 100644
index 00000000..859897d1
--- /dev/null
+++ b/test/speedometer_test.cpp
@@ -0,0 +1,90 @@
+/* vim:set ts=2 sw=2 sts=2 et: */
+/**
+ * \author     Marcus Holland-Moritz (github@mhxnet.de)
+ * \copyright  Copyright (c) Marcus Holland-Moritz
+ *
+ * This file is part of dwarfs.
+ *
+ * dwarfs is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * dwarfs is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with dwarfs.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+#include "dwarfs/speedometer.h"
+
+using namespace dwarfs;
+
+namespace {
+
+class mock_clock {
+ public:
+  using duration = std::chrono::microseconds;
+  using time_point = std::chrono::time_point<mock_clock>;
+
+  static time_point now() { return now_; }
+
+  static void advance(duration d) { now_ += d; }
+
+ private:
+  static thread_local inline time_point now_;
+};
+
+template <typename T>
+using test_speedometer = basic_speedometer<mock_clock, T>;
+
+} // namespace
+
+TEST(speedometer_test, basic) {
+  using namespace std::chrono_literals;
+
+  test_speedometer<int> s{2s};
+
+  EXPECT_EQ(0, s.num_per_second());
+
+  mock_clock::advance(250ms);
+  s.put(10000);
+
+  EXPECT_EQ(0, s.num_per_second());
+
+  mock_clock::advance(250ms); // [250ms, 500ms]
+  s.put(20000);               // [10000 -> 20000]
+
+  EXPECT_EQ(40000, s.num_per_second());
+
+  mock_clock::advance(750ms); // [250ms, 1250ms]
+  s.put(90000);               // [10000 -> 90000]
+
+  EXPECT_EQ(80000, s.num_per_second());
+
+  mock_clock::advance(500ms); // [250ms, 1750ms]
+  s.put(115000);              // [10000 -> 115000]
+
+  EXPECT_EQ(70000, s.num_per_second());
+
+  mock_clock::advance(500ms); // [250ms, 2250ms]
+  s.put(130000);              // [10000 -> 130000]
+
+  EXPECT_EQ(60000, s.num_per_second());
+
+  mock_clock::advance(500ms); // [1250ms, 2750ms]
+  s.put(150000);              // [90000 -> 150000]
+
+  EXPECT_EQ(40000, s.num_per_second());
+
+  mock_clock::advance(750ms); // [1750ms, 3500ms]
+  s.put(176250);              // [115000 -> 176250]
+
+  EXPECT_EQ(35000, s.num_per_second());
+}