diff --git a/tests/testWorld.cpp b/tests/testWorld.cpp
new file mode 100644
index 0000000..2f443b2
--- /dev/null
+++ b/tests/testWorld.cpp
@@ -0,0 +1,51 @@
+#include "testHarness.h"
+#include "vf/World.h"
+
+using namespace vf;
+
+VF_TEST(worldFloorDivHandlesNegatives) {
+    CHECK_EQ(floorDiv(0, 16), 0);
+    CHECK_EQ(floorDiv(15, 16), 0);
+    CHECK_EQ(floorDiv(16, 16), 1);
+    CHECK_EQ(floorDiv(-1, 16), -1);
+    CHECK_EQ(floorDiv(-16, 16), -1);
+    CHECK_EQ(floorDiv(-17, 16), -2);
+}
+
+VF_TEST(worldFloorModHandlesNegatives) {
+    CHECK_EQ(floorMod(0, 16), 0);
+    CHECK_EQ(floorMod(-1, 16), 15);
+    CHECK_EQ(floorMod(16, 16), 0);
+    CHECK_EQ(floorMod(-17, 16), 15);
+}
+
+VF_TEST(worldSetGetCrossesChunkBorders) {
+    World world;
+    world.setBlock(0, 0, 0, Block::Stone);
+    world.setBlock(-1, 5, 3, Block::Grass);
+    world.setBlock(31, 40, 17, Block::Sand);
+
+    CHECK(world.blockAt(0, 0, 0) == Block::Stone);
+    CHECK(world.blockAt(-1, 5, 3) == Block::Grass);
+    CHECK(world.blockAt(31, 40, 17) == Block::Sand);
+    CHECK(world.blockAt(100, 100, 100) == Block::Air);
+}
+
+VF_TEST(worldNegativeCoordinateLandsInExpectedChunk) {
+    World world;
+    world.setBlock(-1, -1, -1, Block::Wood);
+    const Chunk* chunk = world.chunkAt({-1, -1, -1});
+    CHECK(chunk != nullptr);
+    CHECK(chunk->at(15, 15, 15) == Block::Wood);
+    CHECK(world.solidAt(-1, -1, -1));
+}
+
+VF_TEST(worldEnsureChunkIsIdempotent) {
+    World world;
+    Chunk& first = world.ensureChunk({2, 0, 2});
+    first.set(1, 1, 1, Block::Dirt);
+    Chunk& second = world.ensureChunk({2, 0, 2});
+    CHECK(&first == &second);
+    CHECK_EQ(world.chunkCount(), static_cast<std::size_t>(1));
+    CHECK(second.at(1, 1, 1) == Block::Dirt);
+}