From e918966a44affd900076f3c7c9bdcd5323a63352 Mon Sep 17 00:00:00 2001
From: DualFroz <me@dualfroz.com>
Date: Thu, 27 Aug 2026 23:08:43 +0200
Subject: [PATCH] test: add tests for water and lava fluid spread simulation

---
 tests/testFluid.cpp | 92 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 tests/testFluid.cpp

diff --git a/tests/testFluid.cpp b/tests/testFluid.cpp
new file mode 100644
index 0000000..5c8fca8
--- /dev/null
+++ b/tests/testFluid.cpp
@@ -0,0 +1,92 @@
+#include "testHarness.h"
+#include "vf/Fluid.h"
+
+using namespace vf;
+
+namespace {
+
+void solidLayer(World& world, int y, Vec3i lo, Vec3i hi) {
+    for (int x = lo.x; x <= hi.x; ++x)
+        for (int z = lo.z; z <= hi.z; ++z)
+            world.setBlock(x, y, z, Block::Stone);
+}
+
+uint8_t maxWater(const FluidSim& sim) {
+    uint8_t hi = 0;
+    for (uint8_t v : sim.levels()) hi = v > hi ? v : hi;
+    return hi;
+}
+
+} // namespace
+
+VF_TEST(fluidSpreadsWithDecreasingLevelsSymmetrically) {
+    World world;
+    solidLayer(world, 0, {0, 0, 0}, {12, 0, 12});
+    FluidSim sim(world, {0, 0, 0}, {13, 3, 13});
+    sim.addSource(6, 1, 6);
+    int steps = sim.settle(50);
+    CHECK(steps < 50);   // reaches a stable pool
+
+    CHECK_EQ(static_cast<int>(sim.level(6, 1, 6)), fluidMax);
+    CHECK_EQ(static_cast<int>(sim.level(7, 1, 6)), fluidMax - 1);
+    CHECK_EQ(static_cast<int>(sim.level(5, 1, 6)), fluidMax - 1);   // symmetry -x
+    CHECK_EQ(static_cast<int>(sim.level(6, 1, 7)), fluidMax - 1);   // symmetry +z
+    CHECK_EQ(static_cast<int>(sim.level(9, 1, 6)), fluidMax - 3);
+    CHECK_EQ(static_cast<int>(sim.level(10, 1, 10)), 0);   // beyond reach
+    CHECK_EQ(static_cast<int>(sim.level(6, 2, 6)), 0);     // pool stays one deep
+}
+
+VF_TEST(fluidFallsThroughHoleAndSpreadsBelow) {
+    World world;
+    solidLayer(world, 0, {0, 0, 0}, {12, 0, 12});   // lower floor
+    solidLayer(world, 4, {0, 4, 0}, {12, 4, 12});   // upper floor
+    world.setBlock(6, 4, 6, Block::Air);            // hole in the upper floor
+    FluidSim sim(world, {0, 0, 0}, {13, 6, 13});
+    sim.addSource(3, 5, 6);
+    sim.settle(80);
+
+    CHECK_EQ(static_cast<int>(sim.level(6, 2, 6)), fluidMax);   // falling column is full
+    CHECK_EQ(static_cast<int>(sim.level(6, 1, 6)), fluidMax);   // landed on lower floor
+    CHECK(sim.level(7, 1, 6) > 0);   // spreads across the lower floor
+    CHECK(sim.level(8, 1, 6) > 0);
+}
+
+VF_TEST(fluidDrainsAfterSourceRemoved) {
+    World world;
+    solidLayer(world, 0, {0, 0, 0}, {12, 0, 12});
+    FluidSim sim(world, {0, 0, 0}, {13, 3, 13});
+    sim.addSource(6, 1, 6);
+    sim.settle(50);
+    CHECK(maxWater(sim) == fluidMax);
+
+    sim.removeSource(6, 1, 6);
+    int steps = sim.settle(50);
+    CHECK(steps < 50);
+    CHECK_EQ(static_cast<int>(maxWater(sim)), 0);   // pool fully drained
+}
+
+VF_TEST(fluidIsDeterministic) {
+    World worldA, worldB;
+    solidLayer(worldA, 0, {0, 0, 0}, {12, 0, 12});
+    solidLayer(worldB, 0, {0, 0, 0}, {12, 0, 12});
+    FluidSim a(worldA, {0, 0, 0}, {13, 3, 13});
+    FluidSim b(worldB, {0, 0, 0}, {13, 3, 13});
+    a.addSource(6, 1, 6);
+    b.addSource(6, 1, 6);
+    a.settle(50);
+    b.settle(50);
+    CHECK(a.levels() == b.levels());
+}
+
+VF_TEST(fluidBlockedBySolidWall) {
+    World world;
+    solidLayer(world, 0, {0, 0, 0}, {12, 0, 12});
+    for (int y = 1; y <= 2; ++y)
+        for (int z = 0; z <= 12; ++z)
+            world.setBlock(8, y, z, Block::Stone);   // wall at x=8
+    FluidSim sim(world, {0, 0, 0}, {13, 3, 13});
+    sim.addSource(6, 1, 6);
+    sim.settle(50);
+    CHECK(sim.level(7, 1, 6) > 0);              // wet up to the wall
+    CHECK_EQ(static_cast<int>(sim.level(9, 1, 6)), 0);   // nothing past the wall
+}