How we test

Every machine on Contraptify runs in a simulator that follows Java Edition 26.3's own redstone rules, with the game's default settings: block update order, scheduled ticks with priorities, piston timing, quasi-connectivity and torch burnout. Your AI writes a test for each machine from what you asked for: what a player does and when, and what must happen then. The simulator runs it tick by tick and reports what holds and what doesn't, and the AI fixes the design until it all holds.

339 reference tests

Each test builds a small circuit and checks the simulator against known game behaviour. All of them pass on every change before it goes live.

Dust strength 5

dust next to a lever is 15
loses one level per block
16th dust is 0
dust has no delay (same tick)
turns off at once

Weak and strong power 3

dust does not pass through a block it powers
a weakly powered block lights a lamp next to it
a strongly powered block powers dust next to it

Timing 6

repeater delay 1 turns on after 2 game ticks
repeater delay 2 turns on after 4 game ticks
repeater delay 3 turns on after 6 game ticks
repeater delay 4 turns on after 8 game ticks
a torch starts lit
a torch turns off 2 game ticks after its block is powered

Repeater locking 2

a locked repeater ignores its input
it catches up once unlocked

Transparent blocks 5

power climbs onto glass
but does not come down off glass
glass does not pass power to a lamp beside it
a solid block above the lower dust cuts the step up
glass above the lower dust doesn't cut it

Torch burnout 4

a fast torch clock burns out
and stays off while burnt out
with no block update it stays out (its own update took the place of the 160-tick recovery tick)
a block update relights it once its toggles are more than 60 ticks old

Pistons 17

a piston fires in the same tick it is powered
the pushed block is moving for 2 ticks
then lands
13 blocks are too many to push
12 blocks can be pushed
obsidian can't be pushed
blocks with inventories (dispensers) can't be pushed
dust in the way is broken
slime drags the blocks stuck to it
slime and honey don't stick to each other
piston leaves the block
sticky_piston pulls the block back
a lever on top of a sideways piston pops off when it extends
so does a torch on its side
a standing torch on top of it stays (it needs only the middle of the face)
a lever on its back stays while it retracts
and after it has retracted

Quasi-connectivity 4

BUD: the piston stays retracted after the lever is switched on
and extends as soon as it gets a block update
dispensers are quasi-connected too: no shot without an update
one shot after an update

Observers 3

an observer pulses for 2 ticks, starting 2 ticks after the change
an observer moved by a piston pulses once after landing
a sticky piston given a 2-tick observer pulse leaves its block behind

Flying machine 1

it flies and stays in one piece

Comparators reading containers 11

an empty chest reads 0
one item in a chest reads 1
a chest with 2 full stacks reads 2
a full chest reads 15
a full barrel reads 15
a trapped chest with 14 stacks reads 8
a hopper with 1 full stack reads 3
a dropper with 9 eggs reads 1
16 eggs count as a full stack (a dropper with 2 stacks of eggs reads 4)
one sword fills a hopper slot (reads 3)
a comparator reads a chest through a solid block

Hoppers 12

a hopper pulls at once, then items move one hopper every 8 ticks
all three items arrive
items cross three hoppers in 8-tick steps
a hopper pushes from its first filled slot into the first slot with room
then into the next slot with room
a hopper does not push into a full container
a powered hopper is locked and moves nothing
unlocked, it pulls on the next tick
and pushes 8 ticks later
locked again, it holds
dust stays on a hopper and carries power
the dust on top locks the hopper

Droppers 8

a dropper moves one item 4 ticks after it is powered
a comparator reads the chest it filled
one item per press, and nothing once it is empty
a comparator reads 1 from a dropper with one item
the dropper throws its last item and the comparator turns off
the hopper passes a dropped item on 7 ticks after it arrives
a hopper next to a strongly powered block stays locked while the button is down
it unlocks when the button pops up

Trapped chests 2

dust connects to a trapped chest
a closed trapped chest gives no power (the lamp beyond stays off)

Pressure plates 14

stone_pressure_plate: a player on it gives 15 at once
stone_pressure_plate: it strongly powers the block under it
stone_pressure_plate: it checks every 20 ticks, so it lets go 15 ticks after the player steps off
stone_pressure_plate: the dust and the lamp turn off
wooden_pressure_plate: a player on it gives 15 at once
wooden_pressure_plate: it strongly powers the block under it
wooden_pressure_plate: it checks every 20 ticks, so it lets go 15 ticks after the player steps off
wooden_pressure_plate: the dust and the lamp turn off
light_weighted_pressure_plate: one player gives power 1
light_weighted_pressure_plate: it checks every 10 ticks
heavy_weighted_pressure_plate: one player gives power 1
heavy_weighted_pressure_plate: it checks every 10 ticks
a player moving to another plate presses it at once
the first plate lets go at its next check

Target blocks 8

dust points into a target block
powered dust powers a target block like a solid block (the lamp beside it lights)
a thrown snowball has not hit yet
a snowball in the middle of a face gives 15 on the next tick
it is still on 7 ticks after the first hit
it turns off 8 ticks after the first hit, even after a second hit
the hit target gives 15
pushed by a piston, it lands without power

Daylight detectors 6

a daylight detector waits for the game time to reach a multiple of 20
then it gives the sky's power (15 at time 4300)
at time 3020 it gives 13
a right-click inverts it and it checks at once (0 by day)
inverted, it gives 11 at midnight
at dusk (13680) it gives 0

Tripwire 9

hooks facing each other with string between are attached
a player in the string powers both hooks at once
a powered hook strongly powers the block it hangs on (the lamps light)
the hooks stay on while the player stays
the string checks every 10 ticks, so the hooks turn off 5 ticks after the player leaves
a stone block in the line: nothing is attached
so the string doesn't power the hooks
string broken by a piston powers the hooks
10 ticks later they are off and no longer attached

Lecterns 7

a comparator reads page 1 of 5 as 1
turning the page powers the lectern at once
it strongly powers the block under it (the lamp lights)
the pulse lasts 2 ticks
page 2 of 5 reads 4
the last page reads 15
past the last page nothing happens

Sculk sensors 40

a vibration travels 1 block per tick: not yet after 2 ticks
it arrives after 3 ticks: the sensor is active with power 10 (15 - floor(15 / 8 x 3))
a comparator reads the frequency: 10 for a lever turned on
it stays active for 30 ticks
then it cools down with power 0
the comparator reads 0 while it cools down
and is inactive again 10 ticks later
a lever turned off has frequency 9
9 blocks away is out of range
8 blocks away is heard, with power 1
of two vibrations in the same tick, the nearer one wins
a vibration on its way blocks later ones
the far lever's vibration arrives after 8 ticks, power 1
a lever out of range is not heard
a piston breaking a block gives a vibration there (block_destroy, nearer than the piston)
its frequency is 12
a piston retracting gives frequency 9 at the piston (power 8)
wool between a lever and a sensor blocks the vibration
wool next to the line does not
two wool blocks that meet at the line's corner block it
one of them does not
the near sensor hears the lever (power 2)
a sensor activating gives no vibration
a piston can't push a sculk sensor
an active sensor lights a lamp above it and one beside it
it strongly powers the block it stands on (a lamp beside that block lights)
the dust behind it is at 9
it doesn't hear a button pressed (frequency 10)
it hears the button pop up (frequency 9), with power 14 (range 16)
a calibrated sensor stays active for 10 ticks
then cools down
it hears up to 16 blocks: 12 blocks gives power 4
it powers its sides, front and top
but not the block behind it
and strongly powers the block it stands on
a snowball landing on a target 3 blocks up: frequency 2, heard 3 ticks after the hit
switching a daylight detector: frequency 11
a player stepping on a pressure plate: frequency 10
tripwire: not yet after 4 ticks
the hooks 5 blocks away are heard (power 6)

Doors 14

the design's door is two blocks: a lower and an upper half
a lever opens both halves at once (no delay)
and closes them at once
an iron door doesn't open by hand
power beside the upper half opens the door
a player opens a wooden door
power on an open door: it stays open and is powered
a player closes the powered door (clicking the upper half)
power off: it stays closed
power on again opens it
dust ending beside a door powers it
an observer facing the upper half sees the door open
a piston breaks a door, both halves
a door powers nothing: only the door beside the lever opens

Trapdoors 11

dust stays on a closed top trapdoor
a lever opens a trapdoor at once
the dust on it drops off
it closes when the power goes
an iron trapdoor doesn't open by hand
a lever under a bottom trapdoor opens it, drops off, and the trapdoor closes again at once
a player opens a wooden trapdoor
and closes it while powered
the lever opens the trapdoor
pushed away from the lever it lands unpowered and closes
pulled back beside the lever it opens again

Fence gates 17

a lever opens a fence gate at once
and closes it
a player looking south opens a north gate away from them: it turns to face south
closing keeps the facing
looking across it doesn't turn it
a piston pushes a fence gate
a door opening 3 blocks away is heard: frequency 10
a door closing: frequency 9
a trapdoor opening 3 blocks away is heard: frequency 10
a trapdoor closing: frequency 9
a fence gate opening 3 blocks away is heard: frequency 10
a fence gate closing: frequency 9
a player opening a trapdoor: frequency 10
validation: a door needs the block above it free
validation: a door needs a full top face below
validation: a lever on a door is refused
validation: a door with a full block under it passes

Copper bulbs 8

power turns a copper bulb on at once
a comparator reads a lit bulb as 15
power off: it stays lit
the next power turns it off
and the comparator reads 0
a copper bulb is not a conductor: a repeater into it doesn't light the lamp beside it
a bulb can start lit
pushed next to a redstone block, it toggles off when it lands

Note blocks 11

power plays the note once
power off plays nothing
a player's click raises the note and plays it
after 24 it goes back to 0
high notes: 23, one click to 24, power plays 24
a note block is a conductor: a repeater into it lights the lamp beside it
with a block on top it plays nothing
a note played 3 blocks from a sensor is heard: frequency 10
a note block with a block on top plays no note: the sensor hears nothing
a copper bulb switching makes no vibration
an observer sees a note block's note change

TNT 12

unpowered TNT stays
power lights TNT at once: the block is gone
the lamp beside it stays dark (lit TNT powers nothing)
TNT on its way is not lit yet
TNT pushed next to power lights when it lands
lit by a lever pull it explodes 80 ticks later
lit through dust from a lever, also 80
lit by a repeater during a tick it explodes 79 ticks later
lit by a torch turning on, 79
lit by an observer, 79
lit by a piston landing it (after the entity phase), 80
a test checks up to the explosion tick (lit in tick 12, explodes in 91)

Crafters 16

a comparator reads a crafter's filled slots: 1
power sets it triggered at once
nothing crafted after 3 ticks
4 ticks later it crafts one log into 4 planks, into the chest
it shows crafting for 5 ticks
then stops
the next pulse crafts the last log; the comparator then reads 0
a crafter is a conductor: a repeater into it lights the lamp beside it
no quasi-connectivity: power beside the block above it doesn't trigger it
each recipe crafts its result into the chest (no recipe: nothing; a disabled slot counts as empty)
validation: a hopper feeding a crafter is refused
validation: a torch on a fence post passes
validation: stairs with pistons are refused
validation: TNT and a pressure plate are refused together
validation: TNT and a sculk sensor are refused together
validation: a disabled slot can't hold an item

Building blocks 13

before the levers no lamp is lit
packed ice, soul sand and mud conduct; glowstone, sea lanterns, leaves, fences, walls and stairs don't
what stays on stairs facing north
what stays on stairs (top) facing east
what stays on fence
what stays on leaves
what stays on glowstone
what stays on soul_sand
a repeater can stand on a hopper
dust steps up past glowstone above it, but not past packed ice
validation: a dispenser with eggs and a sculk sensor are refused together
validation: a dropper dropping into the world and a sculk sensor are refused together
validation: a calibrated sensor needs a facing

Rails 28

no rail is powered before the levers
a powered rail line carries power 9 rails, in the same tick
an activator rail line does the same
a rail of the other kind stops the power
the whole line turns off at once
power climbs a slope
power runs down a slope
power from the lower rails doesn't reach a rail one block up
power from the upper rails stops at the step
a rail turned across the line stops the power
dust pointing into a powered rail powers it (and the next one)
the pistons have quasi-connected power but haven't moved
a powered rail turning on updates the blocks next to the block below it
a sloped one also updates those next to the block above it
the opened trapdoors leave the rails in place
a neighbour update breaks them
only the broken powered rail updates the blocks around the block below it
rails need a full top face below them (a hopper counts)
a sloped rail also needs a full top face on the block it rises toward
dust links to a detector rail only
validation: a straight rail line passes
validation: a rail needs a shape
validation: only plain rails curve
validation: a rail whose shape the game would change is refused
validation: a corner of plain rails passes
validation: a junction of plain rails passes (it switches with power)
validation: rails with pistons are refused
validation: a slope needs a block to rise against

Falling blocks 15

sand and gravel start to fall 2 ticks after the block below goes
they land after 8, 11, 16, 22 and 32 ticks for drops of 1, 2, 4, 8 and 16 blocks
a falling block lands on full tops, top slabs, stairs, fences, walls, leaves, hoppers, top trapdoors and sand
it breaks on bottom slabs, dust, torches, levers, rails, repeaters, soul sand, chests, honey and bottom trapdoors
the broken ones are logged
sand stays on a torch
a stack leaves from the bottom, 2 ticks apart
the stack lands as three blocks
the pushed sand falls 2 ticks after it lands and becomes a block on the floor
the observer sees the sand land
sand landing on a piston head that finished moving is followed
sand meeting a block the piston is still moving is flagged
validation: sand with a pressure plate is refused
validation: sand with a hopper is refused
validation: sand with a sculk sensor is refused

Minecarts 27

a minecart on a powered rail that is off stays put
the powered rail pushes it away from the block, east
it rolls about 7 blocks and slows to a crawl
the minecart goes down the slope and stops on the unpowered powered rail
nothing is flagged
it stops against the block (its side 0.49 from its middle)
the minecart goes round both curves and up the boosted slope
it stops against the block at the top
the launched minecart reaches full speed
it goes through the curve and the dip and turns both detector rails on
the detector rail turns on as the minecart reaches it and lights the lamp beside it
it stays on while the cart is on it and turns off at a 20-tick check after
the comparator behind it reads 0 from a plain minecart
a placed minecart turns the detector rail on in the next tick
dust beside it lights a lamp
a T-junction keeps its placed shape until a signal source next to it changes
powered it curves north, unpowered south again
the minecart takes the curve north
a 4-way crossing doesn't switch
a T-junction with a powered rail as its third rail switches
a minecart leaving the rails is flagged
validation: a minecart on a rail passes
validation: a minecart off a rail is refused
validation: minecarts with pressure plates are refused
a design's test can place a minecart on a rail (a detector rail then lights a lamp)
place_cart needs a rail
validation: rails on soul sand with minecarts are refused

Not simulated yet

Items lying in the world, double chests, footsteps and flying items, TNT explosions, minecarts off the rails or bumping into things other than full blocks, and mobs. Machines that need them can't be tested yet. Every reference test that a player can build is also run on a real 26.3 server, which must agree on every block and every container on every tick once the machine is built.