Fail fast on missing terrain assets and recover empty renders

tests/renderer-geometry.test.ts

@@ -0,0 +1,79 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import sharp from "sharp";
+import { OpaqueIndex, QuadBuffer } from "../renderer/mesh-buffers.mjs";
+import { assertTerrainImage } from "../renderer/image-validation.mjs";
+
+test("opaque sections preserve negative coordinates and do not alias adjacent boundaries", () => {
+  const index = new OpaqueIndex(
+    { minX: -32, minZ: -32, maxX: 32, maxZ: 32 },
+    -32,
+    32,
+  );
+  const expected = new Set<string>();
+  for (let x = -32; x <= 32; x++) {
+    for (let y = -32; y <= 32; y++) {
+      for (let z = -32; z <= 32; z++) {
+        if ((x * 3 + y * 7 + z * 11) % 23 === 0) {
+          index.add(x, y, z);
+          expected.add(`${x},${y},${z}`);
+        }
+      }
+    }
+  }
+  for (let x = -33; x <= 49; x++) {
+    for (let y = -33; y <= 49; y++) {
+      for (let z = -33; z <= 49; z++) {
+        assert.equal(index.has(x, y, z), expected.has(`${x},${y},${z}`));
+      }
+    }
+  }
+  index.clear();
+  assert.equal(index.has(0, 0, 0), false);
+});
+
+test("geometry batches retain every quad through growth with valid triangle indices and bounds", () => {
+  const buffer = new QuadBuffer();
+  const face = {
+    positions: new Float64Array([0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 0]),
+    uvs: new Float32Array([0, 0, 1, 0, 0, 1, 1, 1]),
+    normal: [0, 0, -1],
+  };
+  for (let i = 0; i < 4096; i++) buffer.add(face, i - 2048, 64, -1);
+  assert.equal(buffer.full, true);
+  assert.throws(() => buffer.add(face, 0, 0, 0), /full/);
+  const data = buffer.finish();
+  assert.equal(data.positions.length, 4096 * 12);
+  assert.equal(data.indices.length, 4096 * 6);
+  assert.equal(Math.max(...data.indices), 4096 * 4 - 1);
+  assert.deepEqual(
+    [...data.indices.slice(-6)],
+    [16380, 16381, 16382, 16382, 16381, 16383],
+  );
+  assert.deepEqual(data.min, [-2048, 64, -1]);
+  assert.deepEqual(data.max, [2048, 65, -1]);
+});
+
+test("sky-only WebP output is rejected instead of becoming a playable draft", async () => {
+  const sky = await sharp({
+    create: { width: 128, height: 128, channels: 3, background: "#95c4eb" },
+  })
+    .webp({ quality: 85 })
+    .toBuffer();
+  await assert.rejects(
+    assertTerrainImage(sky, "Surface map"),
+    /contains only sky/,
+  );
+});
+
+test("flat textured terrain is accepted even when its colors are nearly uniform", async () => {
+  const terrain = await sharp({
+    create: { width: 128, height: 128, channels: 3, background: "#719447" },
+  })
+    .webp()
+    .toBuffer();
+  assert.equal(
+    await assertTerrainImage(terrain, "Panorama p0, downward face"),
+    64 * 64,
+  );
+});