From 854dcfaf15f0871c73fe9aa9c29dc842bd895549 Mon Sep 17 00:00:00 2001
From: DualFroz <me@dualfroz.com>
Date: Fri, 28 Aug 2026 10:36:55 +0200
Subject: [PATCH] test: add tests for hopper item transfer between containers

---
 tests/testHopper.cpp | 123 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)
 create mode 100644 tests/testHopper.cpp

diff --git a/tests/testHopper.cpp b/tests/testHopper.cpp
new file mode 100644
index 0000000..ebaa9b4
--- /dev/null
+++ b/tests/testHopper.cpp
@@ -0,0 +1,123 @@
+#include "testHarness.h"
+#include "vf/Hopper.h"
+
+using namespace vf;
+
+VF_TEST(hopperPullsFromContainerAboveOneItemPerCycle) {
+    World world;
+    Vec3i pos{5, 4, 5};
+    world.setBlock(pos.x, pos.y, pos.z, Block::Hopper);
+
+    ContainerStore store;
+    store.ensure(pos + Vec3i{0, 1, 0}, 5).insert(ItemId::Stone, 3);
+
+    HopperState state;
+    CHECK(tickHopper(world, pos, state, store));
+    CHECK_EQ(store.at(pos)->totalItems(), 1);
+    CHECK_EQ(store.at(pos + Vec3i{0, 1, 0})->totalItems(), 2);
+}
+
+VF_TEST(hopperPushesIntoTargetItFaces) {
+    World world;
+    Vec3i pos{5, 4, 5};
+    world.setBlock(pos.x, pos.y, pos.z, Block::Hopper);
+
+    ContainerStore store;
+    store.ensure(pos, hopperSlots).insert(ItemId::Dirt, 4);
+    store.ensure(pos + Vec3i{0, -1, 0}, 5);
+
+    HopperState state;
+    CHECK(tickHopper(world, pos, state, store));
+    CHECK_EQ(store.at(pos + Vec3i{0, -1, 0})->totalItems(), 1);
+    CHECK_EQ(store.at(pos)->totalItems(), 3);
+}
+
+VF_TEST(hopperRespectsCooldownBetweenTransfers) {
+    World world;
+    Vec3i pos{0, 6, 0};
+    world.setBlock(pos.x, pos.y, pos.z, Block::Hopper);
+
+    ContainerStore store;
+    store.ensure(pos + Vec3i{0, 1, 0}, 5).insert(ItemId::Stone, 64);
+
+    HopperState state;
+    CHECK(tickHopper(world, pos, state, store));   // transfer, arms cooldown 8
+    for (int i = 0; i < hopperCooldownTicks; ++i)
+        CHECK(!tickHopper(world, pos, state, store));   // idle while cooldown drains
+    CHECK(tickHopper(world, pos, state, store));   // fires again
+    CHECK_EQ(store.at(pos)->totalItems(), 2);
+}
+
+VF_TEST(hopperDoesNothingWhenSourceEmptyAndNoPushTarget) {
+    World world;
+    Vec3i pos{1, 1, 1};
+    world.setBlock(pos.x, pos.y, pos.z, Block::Hopper);
+
+    ContainerStore store;
+    store.ensure(pos, hopperSlots);
+    store.ensure(pos + Vec3i{0, 1, 0}, 5);   // empty source
+
+    HopperState state;
+    CHECK(!tickHopper(world, pos, state, store));
+    CHECK_EQ(store.at(pos)->totalItems(), 0);
+}
+
+VF_TEST(hopperBlockedWhenTargetIsFull) {
+    World world;
+    Vec3i pos{2, 2, 2};
+    world.setBlock(pos.x, pos.y, pos.z, Block::Hopper);
+
+    ContainerStore store;
+    store.ensure(pos, hopperSlots).insert(ItemId::Stone, 5);
+    Container& target = store.ensure(pos + Vec3i{0, -1, 0}, 1);
+    target.insert(ItemId::Stone, 64);   // exactly full
+
+    HopperState state;
+    CHECK(!tickHopper(world, pos, state, store));
+    CHECK_EQ(target.totalItems(), 64);
+    CHECK_EQ(store.at(pos)->totalItems(), 5);
+}
+
+VF_TEST(hopperIgnoredWhenWorldBlockIsNotAHopper) {
+    World world;
+    Vec3i pos{3, 3, 3};
+    world.setBlock(pos.x, pos.y, pos.z, Block::Air);
+
+    ContainerStore store;
+    store.ensure(pos + Vec3i{0, 1, 0}, 5).insert(ItemId::Stone, 5);
+
+    HopperState state;
+    CHECK(!tickHopper(world, pos, state, store));
+    CHECK(store.at(pos) == nullptr);
+}
+
+VF_TEST(hopperCanTransferReportsReadiness) {
+    World world;
+    Vec3i pos{7, 7, 7};
+    world.setBlock(pos.x, pos.y, pos.z, Block::Hopper);
+
+    ContainerStore store;
+    store.ensure(pos, hopperSlots);
+    HopperState state;
+    CHECK(!hopperCanTransfer(pos, state, store));
+
+    store.ensure(pos + Vec3i{0, 1, 0}, 5).insert(ItemId::Stone, 1);
+    CHECK(hopperCanTransfer(pos, state, store));
+}
+
+VF_TEST(hopperChainMovesEntireStackAcrossManyCycles) {
+    World world;
+    Vec3i pos{4, 4, 4};
+    world.setBlock(pos.x, pos.y, pos.z, Block::Hopper);
+
+    ContainerStore store;
+    store.ensure(pos + Vec3i{0, 1, 0}, 5).insert(ItemId::Stone, 5);
+    store.ensure(pos + Vec3i{0, -1, 0}, 5);
+
+    HopperState state;
+    for (int tick = 0; tick < 100; ++tick)
+        tickHopper(world, pos, state, store);
+
+    CHECK_EQ(store.at(pos + Vec3i{0, 1, 0})->totalItems(), 0);
+    CHECK_EQ(store.at(pos + Vec3i{0, -1, 0})->totalItems(), 5);
+}