diff --git a/tests/testSpawning.cpp b/tests/testSpawning.cpp
new file mode 100644
index 0000000..bb4bc1c
--- /dev/null
+++ b/tests/testSpawning.cpp
@@ -0,0 +1,158 @@
+#include "testHarness.h"
+#include "vf/Spawning.h"
+
+#include <string>
+#include <vector>
+
+using namespace vf;
+
+namespace {
+
+constexpr int floorY = 64;
+constexpr int spawnY = 65;
+constexpr int fieldSpan = 48;
+
+// One flat plate of `surface` with the sky wide open above it, big enough for
+// the light box below to see nothing but that plate.
+World plateWorld(Block surface) {
+    World world;
+    for (int x = -fieldSpan; x <= fieldSpan; ++x) {
+        for (int z = -fieldSpan; z <= fieldSpan; ++z) world.setBlock(x, floorY, z, surface);
+    }
+    return world;
+}
+
+LightField bakeLight(const World& world) {
+    return computeLight(world, Vec3i{-fieldSpan, floorY - 2, -fieldSpan},
+                        Vec3i{fieldSpan * 2 + 1, 10, fieldSpan * 2 + 1});
+}
+
+SpawnEnvironment nightEnvironment(const World& world, const LightField& light) {
+    SpawnEnvironment env;
+    env.world = &world;
+    env.light = &light;
+    env.dimension = DimensionId::Overworld;
+    env.fallbackBiome = BiomeKind::Plains;
+    env.daytime = false;
+    env.playerPresent = true;
+    env.playerPosition = {40.5f, static_cast<float>(spawnY), 0.5f};
+    env.loadedChunks = 289;
+    env.topY = 70;
+    env.bottomY = 61;
+    return env;
+}
+
+SpawnRule zombieRule() {
+    std::vector<SpawnRule> rules = defaultSpawnRules();
+    return *findSpawnRule(rules, Species::Zombie);
+}
+
+SpawnRule sheepRule() {
+    std::vector<SpawnRule> rules = defaultSpawnRules();
+    return *findSpawnRule(rules, Species::Sheep);
+}
+
+Vec3i originCell() { return Vec3i{0, spawnY, 0}; }
+
+} // namespace
+
+VF_TEST(theStockRuleTableCoversEverySpeciesWithACoherentCategory) {
+    std::vector<SpawnRule> rules = defaultSpawnRules();
+    CHECK_EQ(rules.size(), 6u);
+
+    for (int index = 0; index < static_cast<int>(Species::Count); ++index) {
+        Species species = static_cast<Species>(index);
+        const SpawnRule* rule = findSpawnRule(rules, species);
+        CHECK(rule != nullptr);
+        if (rule == nullptr) continue;
+        CHECK(rule->category == categoryForSpecies(species));
+        CHECK(rule->packMin >= 1);
+        CHECK(rule->packMax >= rule->packMin);
+        CHECK(rule->weight > 0);
+    }
+
+    CHECK(findSpawnRule(rules, Species::Zombie)->dayAllowed == false);
+    CHECK(findSpawnRule(rules, Species::Sheep)->dayAllowed);
+    CHECK(std::string(spawnCategoryName(SpawnCategory::Water)) == std::string("water"));
+    CHECK(std::string(spawnCategoryName(SpawnCategory::Ambient)) == std::string("ambient"));
+
+    for (int index = 0; index < spawnDenialCount; ++index) {
+        SpawnDenial denial = static_cast<SpawnDenial>(index);
+        CHECK(std::string(spawnDenialName(denial)) != std::string("unknown"));
+    }
+}
+
+VF_TEST(aCellThatSatisfiesEveryConditionIsAccepted) {
+    World world = plateWorld(Block::Grass);
+    LightField light = bakeLight(world);
+    SpawnEnvironment env = nightEnvironment(world, light);
+    MobCap cap;
+
+    CHECK_EQ(env.skyLightAt(originCell()), 4);
+    CHECK_EQ(env.blockLightAt(originCell()), 0);
+    CHECK(checkSpawnRule(zombieRule(), env, originCell(), cap) == SpawnDenial::None);
+}
+
+VF_TEST(aFullCategoryCapRefusesTheSpawnBeforeAnythingElseIsChecked) {
+    World world = plateWorld(Block::Grass);
+    LightField light = bakeLight(world);
+    SpawnEnvironment env = nightEnvironment(world, light);
+    MobCap cap;
+
+    env.population[static_cast<std::size_t>(SpawnCategory::Hostile)] =
+        cap.capFor(SpawnCategory::Hostile, env.loadedChunks);
+    CHECK(checkSpawnRule(zombieRule(), env, originCell(), cap) ==
+          SpawnDenial::CategoryCapReached);
+
+    env.population[static_cast<std::size_t>(SpawnCategory::Hostile)] -= 1;
+    CHECK(checkSpawnRule(zombieRule(), env, originCell(), cap) == SpawnDenial::None);
+}
+
+VF_TEST(aRuleFromAnotherDimensionIsRefused) {
+    World world = plateWorld(Block::Grass);
+    LightField light = bakeLight(world);
+    SpawnEnvironment env = nightEnvironment(world, light);
+    env.dimension = DimensionId::Nether;
+    CHECK(checkSpawnRule(zombieRule(), env, originCell(), MobCap{}) ==
+          SpawnDenial::WrongDimension);
+}
+
+VF_TEST(aCellOutsideTheRulesHeightBandIsRefused) {
+    World world = plateWorld(Block::Grass);
+    LightField light = bakeLight(world);
+    SpawnEnvironment env = nightEnvironment(world, light);
+
+    SpawnRule rule = zombieRule();
+    rule.minY = spawnY + 4;
+    CHECK(checkSpawnRule(rule, env, originCell(), MobCap{}) == SpawnDenial::HeightOutOfRange);
+
+    rule.minY = 1;
+    rule.maxY = spawnY - 1;
+    CHECK(checkSpawnRule(rule, env, originCell(), MobCap{}) == SpawnDenial::HeightOutOfRange);
+}
+
+VF_TEST(aBiomeOutsideTheRulesListIsRefused) {
+    World world = plateWorld(Block::Grass);
+    LightField light = bakeLight(world);
+    SpawnEnvironment env = nightEnvironment(world, light);
+
+    std::vector<SpawnRule> rules = defaultSpawnRules();
+    SpawnRule creeper = *findSpawnRule(rules, Species::Creeper);
+    CHECK(!creeper.biomes.empty());
+
+    env.fallbackBiome = BiomeKind::Ocean;
+    CHECK(checkSpawnRule(creeper, env, originCell(), MobCap{}) == SpawnDenial::WrongBiome);
+
+    env.fallbackBiome = BiomeKind::Forest;
+    CHECK(checkSpawnRule(creeper, env, originCell(), MobCap{}) == SpawnDenial::None);
+}
+
+VF_TEST(aNocturnalRuleIsRefusedInBroadDaylight) {
+    World world = plateWorld(Block::Grass);
+    LightField light = bakeLight(world);
+    SpawnEnvironment env = nightEnvironment(world, light);
+    env.daytime = true;
+    CHECK(checkSpawnRule(zombieRule(), env, originCell(), MobCap{}) ==
+          SpawnDenial::WrongTimeOfDay);
+}
+