implement simulation shell

src/test/SimulationTest.cpp

@@ -0,0 +1,133 @@
+#include "catch.hpp"
+
+#include "GameConfig.h"
+#include "Simulation.h"
+#include "Tick.h"
+#include "TickDriver.h"
+
+// ---------------------------------------------------------------------------
+// Simulation
+// ---------------------------------------------------------------------------
+
+TEST_CASE("Simulation::currentTick starts at 0", "[simulation]")
+{
+    const GameConfig config;
+    const Simulation sim(config);
+
+    REQUIRE(sim.currentTick() == 0);
+}
+
+TEST_CASE("Simulation::tick increments currentTick by 1", "[simulation]")
+{
+    const GameConfig config;
+    Simulation sim(config);
+
+    sim.tick();
+
+    REQUIRE(sim.currentTick() == 1);
+}
+
+TEST_CASE("Simulation::tick 10 times yields currentTick == 10", "[simulation]")
+{
+    const GameConfig config;
+    Simulation sim(config);
+
+    for (int i = 0; i < 10; ++i)
+    {
+        sim.tick();
+    }
+
+    REQUIRE(sim.currentTick() == 10);
+}
+
+TEST_CASE("Simulation::drainFireEvents returns empty initially", "[simulation]")
+{
+    const GameConfig config;
+    Simulation sim(config);
+
+    REQUIRE(sim.drainFireEvents().empty());
+}
+
+TEST_CASE("Simulation::drainFireEvents clears queue on drain", "[simulation]")
+{
+    const GameConfig config;
+    Simulation sim(config);
+
+    // First drain: empty.
+    sim.drainFireEvents();
+
+    // Second drain must also be empty (not a double-return).
+    REQUIRE(sim.drainFireEvents().empty());
+}
+
+TEST_CASE("Simulation::drainBlueprintDropEvents returns empty initially", "[simulation]")
+{
+    const GameConfig config;
+    Simulation sim(config);
+
+    REQUIRE(sim.drainBlueprintDropEvents().empty());
+}
+
+// ---------------------------------------------------------------------------
+// TickDriver
+// ---------------------------------------------------------------------------
+
+TEST_CASE("TickDriver: 0x speed never produces ticks", "[simulation]")
+{
+    TickDriver driver;
+
+    REQUIRE(driver.advance(100.0, 0.0) == 0);
+    REQUIRE(driver.advance(1000.0, 0.0) == 0);
+}
+
+TEST_CASE("TickDriver: exactly one tick duration at 1x produces 1 tick", "[simulation]")
+{
+    TickDriver driver;
+
+    REQUIRE(driver.advance(kTickDurationMs, 1.0) == 1);
+}
+
+TEST_CASE("TickDriver: two tick durations at 1x produces 2 ticks", "[simulation]")
+{
+    TickDriver driver;
+
+    REQUIRE(driver.advance(2.0 * kTickDurationMs, 1.0) == 2);
+}
+
+TEST_CASE("TickDriver: 4x speed with quarter tick duration produces 1 tick", "[simulation]")
+{
+    TickDriver driver;
+
+    REQUIRE(driver.advance(kTickDurationMs / 4.0, 4.0) == 1);
+}
+
+TEST_CASE("TickDriver: 0.5x speed with double tick duration produces 1 tick", "[simulation]")
+{
+    TickDriver driver;
+
+    REQUIRE(driver.advance(kTickDurationMs / 0.5, 0.5) == 1);
+}
+
+TEST_CASE("TickDriver: accumulator carries partial progress across frames", "[simulation]")
+{
+    TickDriver driver;
+
+    // 60% of a tick — not enough to fire yet.
+    REQUIRE(driver.advance(kTickDurationMs * 0.6, 1.0) == 0);
+
+    // Another 60% — cumulative 120%, so exactly 1 tick fires.
+    REQUIRE(driver.advance(kTickDurationMs * 0.6, 1.0) == 1);
+}
+
+TEST_CASE("TickDriver::reset clears the accumulator", "[simulation]")
+{
+    TickDriver driver;
+
+    // Advance to just below one tick.
+    driver.advance(kTickDurationMs * 0.9, 1.0);
+
+    driver.reset();
+
+    // Nothing in the accumulator: zero elapsed time should not fire.
+    REQUIRE(driver.advance(0.0, 1.0) == 0);
+}