diff --git a/tests/testWorldGen.cpp b/tests/testWorldGen.cpp
new file mode 100644
index 0000000..ea3da78
--- /dev/null
+++ b/tests/testWorldGen.cpp
@@ -0,0 +1,103 @@
+#include "testHarness.h"
+#include "vf/WorldGen.h"
+
+#include <set>
+
+using namespace vf;
+
+VF_TEST(worldGenChunkIsDeterministic) {
+    WorldGen gen;
+    Chunk first, second;
+    gen.generateChunk(first, {2, 1, -3});
+    gen.generateChunk(second, {2, 1, -3});
+    CHECK(first.raw() == second.raw());
+
+    Chunk elsewhere;
+    gen.generateChunk(elsewhere, {2, 1, 4});
+    CHECK(first.raw() != elsewhere.raw());   // different columns differ
+}
+
+VF_TEST(worldGenSurfaceHeightStaysInBounds) {
+    WorldGen gen;
+    int lo = 1 << 30, hi = -(1 << 30);
+    for (int gx = -200; gx <= 200; gx += 7) {
+        for (int gz = -200; gz <= 200; gz += 7) {
+            int h = gen.surfaceHeight(gx, gz);
+            CHECK(h >= 1 && h < gen.settings().maxY);
+            lo = h < lo ? h : lo;
+            hi = h > hi ? h : hi;
+        }
+    }
+    CHECK(hi > lo);   // terrain actually varies
+}
+
+VF_TEST(worldGenProducesSeveralBiomes) {
+    WorldGen gen;
+    std::set<int> seen;
+    for (int gx = -600; gx <= 600; gx += 25)
+        for (int gz = -600; gz <= 600; gz += 25)
+            seen.insert(static_cast<int>(gen.biomeAt(gx, gz)));
+    CHECK(seen.size() >= 3);
+}
+
+VF_TEST(worldGenOceanMatchesLowSurface) {
+    WorldGen gen;
+    int sea = gen.settings().seaLevel;
+    for (int gx = -400; gx <= 400; gx += 13) {
+        for (int gz = -400; gz <= 400; gz += 13) {
+            bool low = gen.surfaceHeight(gx, gz) < sea - 1;
+            bool ocean = gen.biomeAt(gx, gz) == Biome::Ocean;
+            CHECK_EQ(low, ocean);
+        }
+    }
+}
+
+VF_TEST(worldGenCarvesCavesButNotEverything) {
+    WorldGen gen;
+    int caves = 0, solid = 0;
+    for (int gx = 0; gx < 64; gx += 2)
+        for (int gy = 4; gy < 40; gy += 2)
+            for (int gz = 0; gz < 64; gz += 2)
+                (gen.isCave(gx, gy, gz) ? caves : solid) += 1;
+    CHECK(caves > 0);
+    CHECK(solid > caves);   // caves are the minority
+}
+
+VF_TEST(worldGenPlacesOresUnderground) {
+    WorldGen gen;
+    World world;
+    for (int cx = 0; cx < 2; ++cx)
+        for (int cz = 0; cz < 2; ++cz)
+            gen.generateColumn(world, cx, cz);
+
+    int ores = 0;
+    for (int gx = 0; gx < 32; ++gx) {
+        for (int gz = 0; gz < 32; ++gz) {
+            int surface = gen.surfaceHeight(gx, gz);
+            for (int gy = 1; gy < surface; ++gy) {
+                Block b = world.blockAt(gx, gy, gz);
+                if (b == Block::CoalOre || b == Block::IronOre || b == Block::GoldOre) {
+                    ++ores;
+                    CHECK(gy < surface);   // ores are always below the surface
+                }
+            }
+        }
+    }
+    CHECK(ores > 0);
+}
+
+VF_TEST(worldGenPlantsTrees) {
+    WorldGen gen;
+    World world;
+    int wood = 0;
+    for (int cx = 0; cx < 8; ++cx) {
+        for (int cz = 0; cz < 8; ++cz) {
+            gen.generateColumn(world, cx, cz);
+        }
+    }
+    for (const auto& entry : world.allChunks()) {
+        for (Block b : entry.second->raw())
+            if (b == Block::Wood) ++wood;
+    }
+    CHECK(wood > 0);
+}