1 files changed, 22 insertions, 13 deletions

diff --git a/simloop/test/simloop_test.c b/simloop/test/simloop_test.c
index 41f9ac2..e8efd94 100644
--- a/simloop/test/simloop_test.c
+++ b/simloop/test/simloop_test.c
@@ -65,10 +65,14 @@ TEST_CASE(simloop_initial_render_not_retriggered) {
 ///   1. Updates based on the desired update frame rate.
 ///   2. Renders at every loop (provided there are updates).
 TEST_CASE(simloop_no_render_frame_cap) {
-  constexpr int    UPDATE_FPS    = 10;
-  const time_delta EXPECT_UPDATE = sec_to_time_delta(1.0 / (double)UPDATE_FPS);
-  const time_delta STEP          = sec_to_time_delta(1);
-  const time_delta SIM_TIME_SEC  = sec_to_time_delta(30);
+  constexpr int    UPDATE_FPS   = 10; // 100ms delta
+  const time_delta UPDATE_DDT   = sec_to_time_delta(1.0 / (double)UPDATE_FPS);
+  const time_delta STEP         = sec_to_time_delta(1);
+  const time_delta SIM_TIME_SEC = sec_to_time_delta(30);
+
+  // We need simulation time to be an exact multiple of the desired deltas for
+  // the modulo comparisons below.
+  TEST_TRUE((STEP % UPDATE_DDT) == 0);
 
   Timer   timer = {};
   Simloop simloop =
@@ -78,7 +82,7 @@ TEST_CASE(simloop_no_render_frame_cap) {
   for (time_delta t = 0; t < SIM_TIME_SEC; t += STEP) {
     timer_advance(&timer, t);
     simloop_update(&simloop, &simout);
-    const bool expect_update = (t > 0) && ((t % EXPECT_UPDATE) == 0);
+    const bool expect_update = (t > 0) && ((t % UPDATE_DDT) == 0);
     // A render is still expected at time 0.
     TEST_EQUAL(simout.should_render, (t == 0) || expect_update);
     TEST_EQUAL(simout.should_update, expect_update);
@@ -89,12 +93,17 @@ TEST_CASE(simloop_no_render_frame_cap) {
 ///   1. Updates based on the desired update frame rate.
 ///   2. Renders based on the desired render frame rate.
 TEST_CASE(simloop_with_render_frame_cap) {
-  constexpr int    UPDATE_FPS    = 10;
-  constexpr int    RENDER_FPS    = 5;
-  const time_delta EXPECT_UPDATE = sec_to_time_delta(1.0 / (double)UPDATE_FPS);
-  const time_delta EXPECT_RENDER = sec_to_time_delta(1.0 / (double)RENDER_FPS);
-  const time_delta STEP          = sec_to_time_delta(0.1);
-  const time_delta SIM_TIME_SEC  = sec_to_time_delta(30);
+  constexpr int    UPDATE_FPS   = 10; // 100ms delta
+  constexpr int    RENDER_FPS   = 5;  // 200ms delta
+  const time_delta UPDATE_DDT   = sec_to_time_delta(1.0 / (double)UPDATE_FPS);
+  const time_delta RENDER_DDT   = sec_to_time_delta(1.0 / (double)RENDER_FPS);
+  const time_delta STEP         = sec_to_time_delta(0.1); // 100ms
+  const time_delta SIM_TIME_SEC = sec_to_time_delta(30);
+
+  // We need simulation time to be an exact multiple of the desired deltas for
+  // the modulo comparisons below.
+  TEST_TRUE((UPDATE_DDT % STEP) == 0);
+  TEST_TRUE((RENDER_DDT % STEP) == 0);
 
   Timer      timer   = {};
   Simloop    simloop = simloop_make(&(SimloopArgs){
@@ -105,8 +114,8 @@ TEST_CASE(simloop_with_render_frame_cap) {
     timer_advance(&timer, t);
     simloop_update(&simloop, &simout);
     // A render is still expected at time 0.
-    TEST_EQUAL(simout.should_render, (t % EXPECT_RENDER) == 0);
-    TEST_EQUAL(simout.should_update, (t > 0) && ((t % EXPECT_UPDATE) == 0));
+    TEST_EQUAL(simout.should_render, (t % RENDER_DDT) == 0);
+    TEST_EQUAL(simout.should_update, (t > 0) && ((t % UPDATE_DDT) == 0));
   }
 }