diff --git a/tests/test_hazard.py b/tests/test_hazard.py
new file mode 100644
index 0000000..0fade53
--- /dev/null
+++ b/tests/test_hazard.py
@@ -0,0 +1,43 @@
+from game import constants
+from tests.support import makeWorld
+from game.sim.inputCommand import InputCommand
+
+
+spikeLevel = [
+    "     ",
+    "  p  ",
+    "^^^^^",
+    "XXXXX",
+]
+
+safeLevel = [
+    "     ",
+    "  p  ",
+    "     ",
+    "XXXXX",
+]
+
+
+def test_spikesDamagePlayer():
+    world = makeWorld(spikeLevel)
+    for _ in range(12):
+        world.step(InputCommand())
+    assert world.player.hp <= world.player.maxHp - 2
+    assert world.player.iframes > 0
+
+
+def test_noHazardKeepsFullHealth():
+    world = makeWorld(safeLevel)
+    for _ in range(12):
+        world.step(InputCommand())
+    assert world.player.hp == world.player.maxHp
+
+
+def test_iframesPreventDoubleHit():
+    world = makeWorld(spikeLevel)
+    for _ in range(3):
+        world.step(InputCommand())
+    hpAfterFirst = world.player.hp
+    world.step(InputCommand())
+    assert world.player.hp == hpAfterFirst
+    assert world.player.hp < world.player.maxHp
diff --git a/tests/test_ladder.py b/tests/test_ladder.py
new file mode 100644
index 0000000..f401882
--- /dev/null
+++ b/tests/test_ladder.py
@@ -0,0 +1,50 @@
+import pytest
+
+from game import constants
+from tests.support import makeWorld
+from game.sim.inputCommand import InputCommand
+
+
+ladderLevel = [
+    "  H  ",
+    "  H  ",
+    "  H  ",
+    "XXXXX",
+]
+
+
+def seatOnLadder(world):
+    world.player.x = 2 * constants.tileSize
+    world.player.y = 2 * constants.tileSize
+    world.player.vy = 0.0
+
+
+def test_climbLadderReducesHeight():
+    world = makeWorld(ladderLevel)
+    seatOnLadder(world)
+    startY = world.player.y
+    for _ in range(8):
+        world.step(InputCommand(up=True))
+    assert world.player.onLadder
+    assert world.player.y < startY - 6.0
+
+
+def test_ladderHoverIgnoresGravity():
+    world = makeWorld(ladderLevel)
+    seatOnLadder(world)
+    for _ in range(6):
+        world.step(InputCommand(up=True))
+    restingY = world.player.y
+    for _ in range(6):
+        world.step(InputCommand())
+    assert world.player.y == pytest.approx(restingY, abs=0.5)
+
+
+def test_leavingLadderTileDropsClimbState():
+    world = makeWorld(ladderLevel)
+    seatOnLadder(world)
+    world.step(InputCommand(up=True))
+    assert world.player.onLadder
+    world.player.x = 0.0
+    world.step(InputCommand())
+    assert not world.player.onLadder
diff --git a/tests/test_oneway.py b/tests/test_oneway.py
new file mode 100644
index 0000000..7869216
--- /dev/null
+++ b/tests/test_oneway.py
@@ -0,0 +1,67 @@
+import pytest
+
+from game import constants
+from tests.support import makeWorld
+from game.sim.inputCommand import InputCommand
+
+
+def test_landsOnOneWayFromAbove():
+    world = makeWorld([
+        " p    ",
+        "      ",
+        "======",
+        "      ",
+        "XXXXXX",
+    ])
+    for _ in range(30):
+        world.step(InputCommand())
+    player = world.player
+    assert player.onGround
+    assert player.bottom == pytest.approx(2 * constants.tileSize)
+
+
+def test_passesThroughOneWayFromBelow():
+    world = makeWorld([
+        "      ",
+        "======",
+        "      ",
+        " p    ",
+        "XXXXXX",
+    ])
+    minY = world.player.y
+    world.step(InputCommand(jump=True, jumpHeld=True))
+    for _ in range(16):
+        world.step(InputCommand(jumpHeld=True))
+        minY = min(minY, world.player.y)
+    assert minY < constants.tileSize
+
+
+def test_dropThroughOneWay():
+    world = makeWorld([
+        " p    ",
+        "      ",
+        "======",
+        "      ",
+        "XXXXXX",
+    ])
+    for _ in range(30):
+        world.step(InputCommand())
+    assert world.player.bottom == pytest.approx(2 * constants.tileSize)
+    for _ in range(30):
+        world.step(InputCommand(down=True, jump=True))
+    assert world.player.bottom == pytest.approx(4 * constants.tileSize)
+
+
+def test_downWithoutJumpKeepsPlayerOnOneWay():
+    world = makeWorld([
+        " p    ",
+        "      ",
+        "======",
+        "      ",
+        "XXXXXX",
+    ])
+    for _ in range(30):
+        world.step(InputCommand())
+    for _ in range(20):
+        world.step(InputCommand(down=True))
+    assert world.player.bottom == pytest.approx(2 * constants.tileSize)