Testing time (and found some bugs!)

test/time/CMakeLists.txt

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+# 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

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+/**
+ * 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);
+}