Testing time (and found some bugs!)

src/time/time.c

@@ -33,16 +33,18 @@ void timeUpdate(void) {
 
   #if TIME_FIXED ==  0
     #if TIME_SDL2
-      float_t newTime = (float_t)SDL_GetTicks() / 1000.0f;
+      float_t msElapsed = ((float_t)SDL_GetTicks64() / 1000.0f) + TIME_STEP;
-      TIME.dynamicDelta = newTime - TIME.dynamicTime;
+      TIME.dynamicDelta = msElapsed - TIME.dynamicTime;
-      TIME.dynamicTime = newTime;
+      TIME.dynamicTime = msElapsed;
       TIME.dynamicUpdate = true;
     #else
       #error "No time platform defined"
     #endif
 
     assertTrue(TIME.dynamicDelta >= 0.0f, "Time delta is negative");
-    if(TIME.dynamicTime - TIME.time >= TIME_STEP) {
+
+    // Is within 1ms of a full step?
+    if(TIME.dynamicTime - TIME.time >= TIME_STEP * 0.999f) {
       TIME.dynamicUpdate = false;
       TIME.delta = TIME_STEP;
       TIME.time += TIME_STEP;

src/time/time.h

@@ -8,8 +8,7 @@
 #pragma once
 #include "dusk.h"
 
-#define TIME_STEP (1.0f / 60.0f) // 60 Ticks per second (what we are aiming for)
+#define TIME_STEP (16.0f / 1000.0f)
-
 #ifndef TIME_FIXED
   #define TIME_FIXED 0
 #endif

test/CMakeLists.txt

@@ -3,4 +3,5 @@
 # This software is released under the MIT License.
 # https://opensource.org/licenses/MIT
 
+add_subdirectory(time)
 add_subdirectory(util)

test/time/CMakeLists.txt

@@ -0,0 +1,9 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+include(dusktest)
+
+# Tests
+dusktest(test_time.c)

test/time/test_time.c

@@ -0,0 +1,122 @@
+/**
+ * Copyright (c) 2026 Dominic Masters
+ * 
+ * This software is released under the MIT License.
+ * https://opensource.org/licenses/MIT
+ */
+
+#include "dusktest.h"
+#include <SDL2/SDL.h>
+
+// Mocks
+static uint64_t SDL_GETTICKS_TICKS = 0;
+static bool_t SDL_GETTICKS_CALLED = false;
+
+uint64_t SDL_GetTicks64(void) {
+  SDL_GETTICKS_CALLED = true;
+  return SDL_GETTICKS_TICKS;
+}
+
+// Mocked includes
+#include "util/memory.h"
+#include "time/time.h"
+
+// Tests
+static void test_timeInit(void **state) {
+  (void)state;
+  
+  // Fill time with garbage
+  memorySet(&TIME, 0xFF, sizeof(TIME));
+
+  // Init
+  timeInit();
+
+  // Inital struct is set.
+  assert_float_equal(TIME.time, TIME_STEP, 0.0001f);
+  assert_float_equal(TIME.delta, TIME_STEP, 0.0001f);
+  assert_float_equal(TIME.dynamicTime, TIME_STEP, 0.0001f);
+  assert_float_equal(TIME.dynamicDelta, TIME_STEP, 0.0001f);
+  assert_false(TIME.dynamicUpdate);
+}
+
+static void test_timeUpdate(void **state) {
+  (void)state;
+
+  // Init first
+  timeInit();
+
+  // First time update, calls SDL_GetTicks
+  SDL_GETTICKS_TICKS = 14; // Simulate 15ms elapsed (just barely not one step)
+  SDL_GETTICKS_CALLED = false;
+  timeUpdate();
+  assert_true(SDL_GETTICKS_CALLED);
+  assert_true(TIME.dynamicUpdate);
+  assert_float_equal(TIME.dynamicDelta, 0.014f, 0.0001f);
+  assert_float_equal(TIME.dynamicTime, TIME_STEP + TIME.dynamicDelta, 0.0001f);
+  assert_float_equal(TIME.delta, TIME_STEP, 0.0001f); // Not changed
+  assert_float_equal(TIME.time, TIME_STEP, 0.0001f); // Not changed
+
+  // Simulate total 16ms elapsed (2ms more)
+  SDL_GETTICKS_TICKS = 16;
+  SDL_GETTICKS_CALLED = false;
+  timeUpdate();
+  assert_true(SDL_GETTICKS_CALLED);
+  assert_false(TIME.dynamicUpdate);
+  assert_float_equal(TIME.dynamicDelta, 0.002f, 0.0001f);
+  assert_float_equal(TIME.dynamicTime, TIME_STEP * 2, 0.0001f);
+  assert_float_equal(TIME.delta, TIME_STEP, 0.0001f);
+  assert_float_equal(TIME.time, TIME_STEP * 2, 0.0001f); // Stepped once
+
+  // Second test, half step (16 + 8)
+  SDL_GETTICKS_TICKS = 24;
+  SDL_GETTICKS_CALLED = false;
+  timeUpdate();
+  assert_true(SDL_GETTICKS_CALLED);
+  assert_true(TIME.dynamicUpdate);
+  assert_float_equal(TIME.dynamicDelta, 0.008f, 0.0001f);
+  assert_float_equal(TIME.dynamicTime, TIME_STEP + 0.024f, 0.0001f);
+  assert_float_equal(TIME.delta, TIME_STEP, 0.0001f);
+  assert_float_equal(TIME.time, TIME_STEP * 2, 0.0001f);// Unchanged.
+
+  // Third test, another half step, leading to non dynamic update
+  SDL_GETTICKS_TICKS = 32;
+  SDL_GETTICKS_CALLED = false;
+  timeUpdate();
+  assert_true(SDL_GETTICKS_CALLED);
+  assert_false(TIME.dynamicUpdate);
+  assert_float_equal(TIME.dynamicDelta, 0.008f, 0.0001f);
+  assert_float_equal(TIME.dynamicTime, TIME_STEP + 0.032f, 0.0001f);
+  assert_float_equal(TIME.delta, TIME_STEP, 0.0001f); 
+  assert_float_equal(TIME.time, TIME_STEP * 3, 0.0001f);
+
+  // Fourth test, large jump, should only step once
+  SDL_GETTICKS_TICKS = 100; // Simulate 100ms elapsed
+  SDL_GETTICKS_CALLED = false;
+  timeUpdate();
+  assert_true(SDL_GETTICKS_CALLED);
+  assert_false(TIME.dynamicUpdate);
+  assert_float_equal(TIME.dynamicDelta, 0.068f, 0.0001f);
+  assert_float_equal(TIME.dynamicTime, TIME_STEP + 0.100f, 0.0001f);
+  assert_float_equal(TIME.delta, TIME_STEP, 0.0001f); 
+  assert_float_equal(TIME.time, TIME_STEP * 4, 0.0001f);
+
+  // Fifth test, despite a small time passing the game should be trying to catch
+  // and running extra ticks
+  SDL_GETTICKS_TICKS = 104; // Simulate 4ms elapsed
+  SDL_GETTICKS_CALLED = false;
+  timeUpdate();
+  assert_true(SDL_GETTICKS_CALLED);
+  assert_false(TIME.dynamicUpdate);
+  assert_float_equal(TIME.dynamicDelta, 0.004f, 0.0001f);
+  assert_float_equal(TIME.dynamicTime, TIME_STEP + 0.104f, 0.0001f);
+  assert_float_equal(TIME.delta, TIME_STEP, 0.0001f); 
+  assert_float_equal(TIME.time, TIME_STEP * 5, 0.0001f);
+}
+
+int main(int argc, char **argv) {
+  const struct CMUnitTest tests[] = {
+    cmocka_unit_test(test_timeInit),
+    cmocka_unit_test(test_timeUpdate),
+  };
+  return cmocka_run_group_tests(tests, NULL, NULL);
+}