From 7f6a1e4320f1acced9d25622d9f66b6e71098c30 Mon Sep 17 00:00:00 2001
From: DualFroz <me@dualfroz.com>
Date: Sun, 13 Sep 2026 12:41:33 +0200
Subject: [PATCH] test: cover Session and Ledger

---
 tests/testSlotAction.cpp | 156 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 156 insertions(+)
 create mode 100644 tests/testSlotAction.cpp

diff --git a/tests/testSlotAction.cpp b/tests/testSlotAction.cpp
new file mode 100644
index 0000000..c33fe23
--- /dev/null
+++ b/tests/testSlotAction.cpp
@@ -0,0 +1,156 @@
+#include "testHarness.h"
+#include "vf/SlotAction.h"
+
+#include <array>
+#include <string>
+#include <vector>
+
+using namespace vf;
+
+namespace {
+
+const CraftingRegistry& sharedRegistry() {
+    static CraftingRegistry registry;
+    return registry;
+}
+
+struct Session {
+    ContainerMenu menu;
+    CursorStack cursor;
+    DragState drag;
+
+    explicit Session(MenuKind kind) : menu(kind, &sharedRegistry()) {}
+
+    SlotActionResult click(ClickKind kind, int slotIndex) {
+        return applySlotAction(menu, cursor, drag, clickAt(kind, slotIndex));
+    }
+    SlotActionResult hotbar(int slotIndex, int button) {
+        return applySlotAction(menu, cursor, drag, hotbarSwapAt(slotIndex, button));
+    }
+};
+
+// The seven items the random walk shuffles around. Tools are in the mix so the
+// walk also has stacks that refuse to merge.
+const std::array<ItemId, 7> walkItems = {ItemId::Stone,     ItemId::Planks, ItemId::Sand,
+                                         ItemId::CoalLump,  ItemId::Apple,  ItemId::IronPickaxe,
+                                         ItemId::RawBeef};
+
+struct Ledger {
+    std::array<int, 7> counts{};
+
+    void snapshot(const ContainerMenu& menu, const CursorStack& cursor) {
+        for (std::size_t i = 0; i < walkItems.size(); ++i) {
+            counts[i] = totalAcrossMenuAndCursor(menu, cursor, walkItems[i]);
+        }
+    }
+};
+
+void seedMenu(ContainerMenu& menu, uint32_t& rng) {
+    for (int i = 0; i < menu.slotCount(); ++i) {
+        if (menu.slot(i).takeOnly) continue;
+        if (stackRandom(rng) % 3u == 0u) continue;
+        ItemId item = walkItems[stackRandom(rng) % walkItems.size()];
+        MetaStack stack = makeStack(item, 1 + static_cast<int>(stackRandom(rng) % 40u));
+        if (!menu.canPlace(i, stack)) continue;
+        menu.slot(i).cell.insert(stack);
+    }
+}
+
+SlotAction randomAction(const ContainerMenu& menu, uint32_t& rng) {
+    ClickKind kind = static_cast<ClickKind>(stackRandom(rng) %
+                                            static_cast<uint32_t>(ClickKind::Count));
+    int slotIndex = static_cast<int>(stackRandom(rng) % static_cast<uint32_t>(menu.slotCount()));
+    // Every eighth action aims outside the window, which is the only way to
+    // reach the throw-away path with a full cursor.
+    if (stackRandom(rng) % 8u == 0u) slotIndex = -1;
+    if (kind == ClickKind::HotbarSwap) {
+        return hotbarSwapAt(slotIndex, static_cast<int>(stackRandom(rng) % 9u));
+    }
+    return clickAt(kind, slotIndex);
+}
+
+struct WalkCoverage {
+    int applied = 0;
+    int dropped = 0;
+    int distinctKindsApplied = 0;
+};
+
+WalkCoverage runConservationWalk(MenuKind kind, uint32_t seed, int steps) {
+    Session session(kind);
+    uint32_t rng = seed;
+    seedMenu(session.menu, rng);
+
+    Ledger before;
+    before.snapshot(session.menu, session.cursor);
+
+    std::array<int, 7> thrown{};
+    std::array<int, static_cast<std::size_t>(ClickKind::Count)> perKind{};
+    WalkCoverage coverage;
+    for (int step = 0; step < steps; ++step) {
+        SlotAction action = randomAction(session.menu, rng);
+        SlotActionResult outcome =
+            applySlotAction(session.menu, session.cursor, session.drag, action);
+        if (outcome.applied) {
+            ++coverage.applied;
+            ++perKind[static_cast<std::size_t>(action.kind)];
+        }
+        coverage.dropped += outcome.dropped;
+        CHECK_EQ(outcome.created, 0);
+        CHECK_EQ(outcome.dropped, static_cast<int>([&] {
+                     int sum = 0;
+                     for (const MetaStack& lost : outcome.droppedStacks) sum += lost.count;
+                     return sum;
+                 }()));
+        for (const MetaStack& lost : outcome.droppedStacks) {
+            for (std::size_t i = 0; i < walkItems.size(); ++i) {
+                if (lost.item == walkItems[i]) thrown[i] += lost.count;
+            }
+        }
+    }
+
+    Ledger after;
+    after.snapshot(session.menu, session.cursor);
+    for (std::size_t i = 0; i < walkItems.size(); ++i) {
+        CHECK_EQ(after.counts[i] + thrown[i], before.counts[i]);
+    }
+    for (int hits : perKind) {
+        if (hits > 0) ++coverage.distinctKindsApplied;
+    }
+    return coverage;
+}
+
+} // namespace
+
+VF_TEST(everyClickKindHasAName) {
+    for (int i = 0; i < static_cast<int>(ClickKind::Count); ++i) {
+        CHECK(std::string(clickKindName(static_cast<ClickKind>(i))) != std::string("unknown"));
+    }
+}
+
+VF_TEST(aLeftClickPicksUpTheWholeStackAndPutsItDownAgain) {
+    Session session(MenuKind::Chest);
+    session.menu.slot(0).cell.stack = makeStack(ItemId::Stone, 37);
+
+    SlotActionResult pickup = session.click(ClickKind::Left, 0);
+    CHECK(pickup.applied);
+    CHECK_EQ(pickup.moved, 37);
+    CHECK(pickup.cursorChanged);
+    CHECK_EQ(session.cursor.held.count, 37);
+    CHECK(session.menu.stackAt(0).empty());
+
+    SlotActionResult drop = session.click(ClickKind::Left, 4);
+    CHECK(drop.applied);
+    CHECK_EQ(drop.moved, 37);
+    CHECK(session.cursor.empty());
+    CHECK_EQ(session.menu.stackAt(4).count, 37);
+
+    CHECK(!session.click(ClickKind::Left, 9).applied);
+    CHECK(!session.click(ClickKind::Left, 999).applied);
+}
+
+VF_TEST(aLeftClickMergesIntoAMatchingStackAndSwapsWithAForeignOne) {
+    Session session(MenuKind::Chest);
+    session.menu.slot(0).cell.stack = makeStack(ItemId::Sand, 50);
+    session.menu.slot(1).cell.stack = makeStack(ItemId::Sand, 60);
+    session.menu.slot(2).cell.stack = makeStack(ItemId::Planks, 8);
+