From 522662ded6dd2f4160d9701205c1678c32f9dbc8 Mon Sep 17 00:00:00 2001
From: DualFroz <me@dualfroz.com>
Date: Sun, 13 Sep 2026 21:12:44 +0200
Subject: [PATCH] test: extend coverage of testTileTexture

---
 tests/testTileTexture.cpp | 140 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+)

diff --git a/tests/testTileTexture.cpp b/tests/testTileTexture.cpp
index 7e3c682..056fff1 100644
--- a/tests/testTileTexture.cpp
+++ b/tests/testTileTexture.cpp
@@ -301,3 +301,143 @@ VF_TEST(writeTileAgreesWithPixelAtEverywhere) {
     }
 }
 
+// The atlas is built at sixteen pixels today, but nothing in the palette is
+// allowed to depend on that. Alpha rules and contrast have to survive a
+// different tile size.
+VF_TEST(tilesKeepTheirAlphaAndContrastAtOtherTileSizes) {
+    const int sizes[] = {8, 16, 32};
+    for (int size : sizes) {
+        TileTextureParams params;
+        params.tileSize = size;
+        TileSampler sampler(params);
+        for (int tile = 0; tile < renderedTiles(sampler); ++tile) {
+            const TileSpec& spec = sampler.palette().specFor(tile);
+            int holes = 0;
+            int solid = 0;
+            for (int y = 0; y < size; ++y) {
+                for (int x = 0; x < size; ++x) {
+                    uint8_t alpha = sampler.pixelAt(tile, x, y).a;
+                    if (alpha == 0) ++holes;
+                    if (alpha == 255) ++solid;
+                }
+            }
+            CHECK_EQ(holes + solid, size * size);
+            if (spec.cutout) {
+                CHECK(holes > 0);
+                CHECK(solid > 0);
+                if (holes == 0 || solid == 0) {
+                    std::printf("  tile %d (%s) at size %d: %d holes, %d solid\n", tile, spec.name,
+                                size, holes, solid);
+                }
+            } else {
+                CHECK_EQ(holes, 0);
+            }
+            int spread = interiorRange(sampler, tile).spread();
+            CHECK(spread >= 8);
+            if (spread < 8) {
+                std::printf("  tile %d (%s) at size %d is flat: spread %d\n", tile, spec.name, size,
+                            spread);
+            }
+        }
+    }
+}
+
+// Boards run one way and their grain runs with them. Flipping the spec's axis
+// has to flip which direction the tile varies in, otherwise the plank pattern
+// is drawing wallpaper.
+VF_TEST(plankGrainFollowsTheBoardDirection) {
+    TileSampler sampler;
+    int size = sampler.params().tileSize;
+
+    TileSpec board;
+    board.name = "testBoard";
+    board.pattern = TilePattern::Plank;
+    board.material = TileMaterial::Wood;
+    board.base = TileRgb{160, 120, 70};
+    board.accent = TileRgb{90, 64, 34};
+    board.noise = 0.0f;
+    board.scale = 0.35f;
+    board.density = 0.50f;
+
+    TileSpec upright = board;
+    upright.vertical = true;
+
+    auto axisSpread = [&](const TileSpec& spec, bool alongColumns) {
+        int lowest = 255;
+        int highest = 0;
+        for (int outer = 1; outer < size; ++outer) {
+            int total = 0;
+            for (int inner = 1; inner < size; ++inner) {
+                int x = alongColumns ? outer : inner;
+                int y = alongColumns ? inner : outer;
+                total += luminance(sampler.pixelOf(spec, 900, x, y));
+            }
+            int mean = total / (size - 1);
+            if (mean < lowest) lowest = mean;
+            if (mean > highest) highest = mean;
+        }
+        return highest - lowest;
+    };
+
+    int uprightAcrossColumns = axisSpread(upright, true);
+    int uprightAcrossRows = axisSpread(upright, false);
+    CHECK(uprightAcrossColumns > uprightAcrossRows);
+
+    int flatAcrossRows = axisSpread(board, false);
+    int flatAcrossColumns = axisSpread(board, true);
+    CHECK(flatAcrossRows > flatAcrossColumns);
+}
+
+// A ladder without gaps is a plank. Every cutout lattice has to leave real
+// openings and still keep enough bar to stand on.
+VF_TEST(latticeTilesLeaveOpeningsBetweenTheirBars) {
+    TileSampler sampler;
+    int size = sampler.params().tileSize;
+    int checked = 0;
+    for (int tile = 0; tile < renderedTiles(sampler); ++tile) {
+        const TileSpec& spec = sampler.palette().specFor(tile);
+        if (spec.pattern != TilePattern::Lattice || !spec.cutout) continue;
+        ++checked;
+        int holes = 0;
+        for (int y = 0; y < size; ++y) {
+            for (int x = 0; x < size; ++x) {
+                if (sampler.pixelAt(tile, x, y).a == 0) ++holes;
+            }
+        }
+        float openFraction = static_cast<float>(holes) / static_cast<float>(size * size);
+        CHECK(openFraction > 0.15f);
+        CHECK(openFraction < 0.92f);
+        if (openFraction <= 0.15f || openFraction >= 0.92f) {
+            std::printf("  tile %d (%s) is %.2f open\n", tile, spec.name,
+                        static_cast<double>(openFraction));
+        }
+    }
+    CHECK(checked >= 8);
+}
+
+// Veins have to be visible without swallowing the host rock, or every ore looks
+// like a solid block of its own metal.
+VF_TEST(oreVeinsCoverPartOfTheHostRockWithoutSwallowingIt) {
+    TileSampler sampler;
+    int size = sampler.params().tileSize;
+    int checked = 0;
+    for (int tile = 0; tile < renderedTiles(sampler); ++tile) {
+        const TileSpec& spec = sampler.palette().specFor(tile);
+        if (spec.pattern != TilePattern::OreSpeckle) continue;
+        ++checked;
+        int vein = 0;
+        for (int y = 0; y < size; ++y) {
+            for (int x = 0; x < size; ++x) {
+                if (leansToAccent(sampler.pixelAt(tile, x, y), spec)) ++vein;
+            }
+        }
+        float coverage = static_cast<float>(vein) / static_cast<float>(size * size);
+        CHECK(coverage > 0.02f);
+        CHECK(coverage < 0.55f);
+        if (coverage <= 0.02f || coverage >= 0.55f) {
+            std::printf("  tile %d (%s) vein coverage %.3f\n", tile, spec.name,
+                        static_cast<double>(coverage));
+        }
+    }
+    CHECK(checked >= 9);
+}