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Version: 1.6.0

Testing LIGO

Testing LIGO code

The LIGO command-line interpreter provides commands to directly test your LIGO code. The three main commands we currently support are:

  • ligo run test

  • ligo run interpret

  • ligo run dry-run

We will show how to use the first two, while an example on how to use the third one was already explained here.

Testing with ligo run test

The command ligo run test can be used to test a contract using LIGO.

⚠️ Please keep in mind that this command is still BETA, and that there are features that are work in progress and are subject to change. No real test procedure should rely on this command alone.

When running the ligo run test command, LIGO code has access to an additional Test module. This module provides ways of originating contracts and executing transactions, as well as additional helper functions that allow to control different parameters of the Tezos testing library.

Note: The LIGO interpreter uses the same library that Tezos internally uses for testing.

The function Test.originate allows to deploy a contract in the testing environment. It takes a contract, which is represented as a function of type 'parameter -> 'storage -> operation list * 'storage, an initial storage of type 'storage, and an initial balance for the contract being deployed. This function deploys the contract, and returns a record value holding: ('parameter, 'storage) typed_address, the compiled program in Michelson of type ('parameter, 'storage) michelson_contract, and the size of the program of type int.

The storage of a deployed contract can be queried using the Test.get_storage function, that given a typed address ('parameter, 'storage) typed_address, returns the 'storage value.

As a concrete example, suppose we have the following contract:

// This is mycontract.jsligo
namespace C {
export type storage = int;
export type result = [list<operation>, storage];
@entry const increment = (delta : int, store : storage) : result => [[], store + delta];
@entry const decrement = (delta : int, store : storage) : result => [[], store - delta];
@entry const reset = (_u : unit, _store : storage) : result => [[], 0];

We can deploy it and query the storage right after, to check that the storage is in fact the one which we started with:

// This is mycontract-test.jligo
#import "gitlab-pages/docs/advanced/src/testing/mycontract.mligo" "MyContract"
type param = parameter_of MyContract.C
const run_test1 = () : unit => {
let initial_storage = 42 as int;
let {addr , code , size} = Test.originate(contract_of(MyContract.C), initial_storage, 0tez);
assert (Test.get_storage(addr) == initial_storage);
const test1 = run_test1();

The ligo run test sub-command will evaluate all top-level definitions and print any entries that begin with the prefix test as well as the value that these definitions evaluate to. If any of the definitions are found to have failed, a message will be issued with the line number where the problem occurred.

ligo run test --library . gitlab-pages/docs/advanced/src/testing/mycontract-test.jsligo
# Outputs:
# Everything at the top-level was executed.
# - test1 exited with value ().

The function Test.transfer allows to bake a transaction. It takes a target account of type ('parameter, 'storage) typed_address, the parameter of type 'parameter and an amount of type tez. This function performs the transaction, and returns a test_exec_result which can be matched on to know whether the transaction was successful or not. In case of success you will get access to the gas consumed by the execution of the contract and in case of failure you will get access to a test_exec_error describing the error. There is an alternative version, called Test.transfer_exn which performs the transaction and will only return the gas consumption, failing in case that there was an error.

We can extend the previous example by executing a transaction that increments the storage after deployment, we also print the gas consumption:

The syntax do { ... } is equivalent to ( () => { ... } )(), i.e. it is a block expression which can contain statements and local declarations.

// This continues mycontract-test.jsligo
const test2 = do {
let initial_storage = 42 as int;
let orig = Test.originate(contract_of (MyContract.C), initial_storage, 0tez);
let gas_cons = Test.transfer_exn(orig.addr, (Increment (1)), 1mutez);
Test.log(["gas consumption", gas_cons]);
return (Test.get_storage(orig.addr) == initial_storage + 1);

The environment assumes a source for the operations which can be set using the function Test.set_source : address -> unit.

Transfers and originations with tickets

Originating contract storing tickets or transfering to contract accepting tickets requires some extra steps. We will first explain the problems with tickets and then show you how to handle it.

The problem with tickets

There is two kind of operations in the protocol : external and internal. internal operations are those created by smart contracts and external operations are those created from outside the chain (e.g. using Test.originate or tezos-client for instance) more information here

In the protocol, both external and internal transfer/origination operations contains a piece of michelson code representing the parameter/initial storage. Now imagine you have a value of type parameter_ty/storage_ty containing a ticket, that you want to transfer or originate, in the operation data, tickets will be represented in Michelson as pairs:

> ligo compile expression cameligo 'Tezos.create_ticket 0x0202 10n'

ticketer address , ticket value , ticket amount

If we try to apply such an operation, the type wouldn't match: ticket of bytes VS some pair. The protocol would not let you do that since you could be creating a ticket out of nowhere unless the operation happens to be forged from within a contract (i.e. "internally")!

In the testing framework - for now - it means using "proxy-contracts" forging the operations using provided a ticket value and a ticket amount.

Proxy ticket contracts

The LIGO standard library provides a Proxy_ticket module which helps in working with tickets in the Testing framework. Here is the interface of Proxy_ticket:

init_transfer accepts:

  • a function mk_param which given a ticket must return a value of your parameter type

and returns the typed address of a "transfer proxy-contract" which can then be used to do multiple transfers of tickets with the same ticketer address

transfer accepts :

  • the typed address of a "transfer proxy-contract"
  • the ticket information (value and amount) together with the destination address

and returns a value of type test_exec_result

originate accepts:

  • the ticket information (value and amount)
  • a function mk_storage which given a ticket must return a value of your storage type
  • your contract (having a ticket in its storage type)

Note: Functions mk_param and mk_storage will be executed in the proxy contract itself

Find more detailed information on the API of Proxy_ticket here



Here is an example using Proxy_ticket.init_transfer and Proxy_ticket.transfer:

  1. import the module above as Proxy_ticket
  2. define a contract C holding a ticket of string in its parameter type. The contract will just store the value of the received ticket and the address of the sender
  3. originate contract C
  4. initialize a "transfer proxy-contract" providing a function to build a parameter out of a ticket
  5. transfer a ticket with a value "hello" and an amount of 10 to contract C
  6. print the storage of contract C
  7. transfer a ticket with a value "world" and an amount of 5 to contract C
  8. print the storage of contract C
namespace C {
export type param = [ int , ticket<string>]
function main (p: param, _s: [string , address]) : [list<operation> , [string , address]] {
let [_v,ticket] = p ;
let [[_addr,[v,_t]] , _ticket] = Tezos.read_ticket (ticket) ;
return ([[] , [v, Tezos.get_sender ()]])
const test_transfer_to_contract = do {
let {addr : main_taddr, code , size } = Test.originate (contract_of(C), ["bye",Test.nth_bootstrap_account (1)], 1mutez) ;
let main_addr = Test.to_address (main_taddr) ;
/* mk_param is executed __by the proxy contract__ */
const mk_param = (t:ticket<string>) : C.param => { return [42,t] } ;
/* Use this address everytime you want to send tickets from the same proxy-contract */
/* initialize a proxy contract in charge of creating and sending your tickets */
let proxy_taddr = Test.Proxy_ticket.init_transfer (mk_param) ;
Test.log (["poxy addr:", proxy_taddr]) ;
/* ticket_info lets you control the amount and the value of the tickets you send */
let ticket_info1 = ["hello", 10n];
/* we send ticket to main through the proxy-contract */
Test.Proxy_ticket.transfer (proxy_taddr, [ticket_info1,main_addr]) ;
Test.log (Test.get_storage (main_taddr)) ;
let ticket_info2 = ["world",5n] ;
Test.Proxy_ticket.transfer (proxy_taddr, [ticket_info2,main_addr]) ;
Test.log (Test.get_storage (main_taddr));


> ligo run test transfer_ticket.mligo
("poxy addr:" , KT1QGANLjYsyJmw1QNww9Jkgb4ccQr6W2gsC)
("hello" , KT1QGANLjYsyJmw1QNww9Jkgb4ccQr6W2gsC)
("world" , KT1QGANLjYsyJmw1QNww9Jkgb4ccQr6W2gsC)
Everything at the top-level was executed.
- test_transfer_to_contract exited with value ().

Note: note that the sender (stored in the contract) matches the address of the proxy contract


Here is an example using Proxy_ticket.originate and the type unforged_ticket :

  1. import the module above as Proxy_ticket
  2. define a contract main potentially holding a ticket of bytes in its storage. The contract will just reads the ticket in its storage if present. Note that we define two version of the contract storage type: one for the contract and one for the storage type that we would like to manipulate in our testing logic
  3. we define the mk_storage function which simply wraps a ticket into an option type
  4. we define the ticket information for a ticket of value 0x0202 and an amount of 15
  5. we call originate and retrieve the address of the newly originated contract
  6. we use the address to fetch the current contract storage using Test.get_storage_of_address and decompile it as a human_storage
  7. we read the content of the ticket and perform a series of assertions
type storage = option< ticket<bytes> >
type unforged_storage = option< unforged_ticket<bytes> >
const main = (_p: unit, s: storage) : [ list<operation> , storage] => {
let x =
match (s) {
when(Some(ticket)): ((ticket: ticket<bytes>) => {
let [_v , t] = Tezos.read_ticket (ticket) ;
return Some (t)
when(None()): None()
return [list ([]), x]
const test_originate_contract = do {
const mk_storage = (t:ticket<bytes>) : storage => { return (Some (t)) } ;
let ticket_info = [0x0202, 15n];
let addr = Test.Proxy_ticket.originate (ticket_info, mk_storage, main) ;
let unforged_storage = (Test.Proxy_ticket.get_storage (addr) as unforged_storage) ;
/* the ticket 'unforged_storage' can be manipulated freely without caring about ticket linearity */
match (unforged_storage) {
when(Some(x)): do {
Test.log (["unforged_ticket", x]) ;
let { ticketer , value , amount } = x ;
assert (value == ticket_info[0]) ;
assert (amount == ticket_info[1]) ;
return unit
when(None()): failwith ("impossible")


("unforged_ticket" , {amount = 15n ; ticketer = KT1Qp8u3v4seQHPYfpSw6eWvPG8CojH3m18G ; value = 0x0202})
Everything at the top-level was executed.
- test_originate_contract exited with value ().

Unit testing a function

Consider a map binding addresses to amounts and a function removing all entries in that map having an amount less to a given threshold.

// This is remove-balance.jsligo
type balances = map <address, tez>
const remove_balances_under = (b : balances, threshold:tez) : balances => {
let f = ([acc, kv] : [balances, [address , tez]] ) : balances => {
let [k,v] = kv ;
if (v < threshold) { return Map.remove (k,acc) } else {return acc}
return Map.fold (f,b,b);

Let us imagine that we want to test this function against a range of thresholds with the LIGO test framework.

First, let's include the file under test and reset the state with 5 bootstrap accounts (we are going to use the bootstrap addresses later)

#include "./gitlab-pages/docs/advanced/src/testing/remove-balance.jsligo"
let _u = Test.reset_state (5n, [] as list <tez>);

Now build the balances map that will serve as the input of our test.

let balances : balances =
Map.literal([[Test.nth_bootstrap_account(1), 10tez],
[Test.nth_bootstrap_account(2), 100tez],
[Test.nth_bootstrap_account(3), 1000tez]]);

Our simple test loop will call remove_balances_under with the compiled map defined above, get the size of the resulting map and compare it to an expected value with Test.michelson_equal.

The call to balance_under and the computation of the size of the resulting map is achieved through the primitive This primitive runs a function on an input, translating both (function and input) to Michelson before running on the Michelson interpreter. More concretely f v performs the following:

  1. Compiles the function argument f to Michelson f_mich
  2. Compiles the value argument v (which was already evaluated) to Michelson v_mich
  3. Runs the Michelson interpreter on the code f_mich with the initial stack [ v_mich ]

The function that is being compiled is called tester.

We also print the actual and expected sizes for good measure.

let test =
( ([threshold , expected_size] : [tez , nat]) : unit => {
let tester = ([balances, threshold] : [balances, tez]) : nat => Map.size (remove_balances_under (balances, threshold));
let size =, [balances, threshold]);
let expected_size_ = Test.eval(expected_size) ;
let unit_ = Test.log (["expected", expected_size]) ;
let unit__ = Test.log (["actual",size]) ;
return (assert (Test.michelson_equal (size,expected_size_)))
list ([ [15tez, 2n] , [130tez, 1n] , [1200tez, 0n]]) );

You can now execute the test:

ligo run test --library . gitlab-pages/docs/advanced/src/testing/unit-remove-balance-mixed.jsligo
# Outputs:
# ("expected" , 2)
# ("actual" , 2)
# ("expected" , 1)
# ("actual" , 1)
# ("expected" , 0)
# ("actual" , 0)
# Everything at the top-level was executed.
# - test exited with value ().

Testing with ligo run interpret

The command ligo run interpret allows to interpret an expression in a context initialised by a source file. The interpretation is done using Michelson's interpreter.

We can see how it works on an example. Suppose we want to test the following contract.

// This is testme.jsligo
type storage = int;
type result = [list<operation>, storage];
@entry const increment = (delta: int, store: storage): result => [[], store + delta];
@entry const decrement = (delta: int, store: storage): result => [[], store - delta];
@entry const reset = (_u: unit, _store: storage): result => [[], 0];

This contract keeps an integer as storage, and has three entry-points: one for incrementing the storage, one for decrementing the storage, and one for resetting the storage to 0.

As a simple property, we check whether starting with a storage of 10, if we execute the entry-point for incrementing 32, then we get a resulting storage of 42. For checking it, we can interpret the main function:

ligo run interpret "increment (32, 10)" --init-file gitlab-pages/docs/advanced/src/testing/testme.jsligo
# Outputs:
# ( LIST_EMPTY() , 42 )

With the argument --init-file we pass the contract we want to test, and the sub-command requires also the expression to evaluate in that context, in this case, a call to our contract (main) with parameter Increment (32) and storage 10. As a result, we can check that the resulting storage is 42 (the second component of the pair), and there are no further operations to execute (the first component).

We can tune certain parameters of the execution by passing them as arguments:

--amount=AMOUNT (absent=0)
AMOUNT is the amount the Michelson interpreter will use for the
--balance=BALANCE (absent=0)
BALANCE is the balance the Michelson interpreter will use for the
contract balance.
NOW is the NOW value the Michelson interpreter will use
(e.g. '2000-01-01T10:10:10Z')
SENDER is the sender the Michelson interpreter transaction will use.
SOURCE is the source the Michelson interpreter transaction will use.

Event testing

Here is how you emit events and fetch them from your tests:

namespace C {
let main = (p: [int, int], _: unit) => {
let op1 = Tezos.emit("%foo", p);
let op2 = Tezos.emit("%foo", p[0]);
return [([op1, op2] as list<operation>), unit];
let test = do {
let orig = Test.originate(contract_of(C), unit, 0tez);
Test.transfer_exn(orig.addr, Main ([1,2]), 0tez);
return [Test.get_last_events_from(orig.addr, "foo") as list<[int, int]>, Test.get_last_events_from(orig.addr, "foo") as list<int>];

Testing a contract declared as a module or namespace

When declaring the entry points of a contract using @entry, LIGO generates two hidden values in the module:

  • an implicit main function, which can be obtained using the keyword contract_of(C) where C is the namespace or module containing the entry points, and
  • the input type for that main function, which can be obtained using the keyword parameter_of C.

In the example below, contract_of(C) is returns the implicitly-declared main function that calls the increment or decrement entry points depending on the argument given, and parameter_of C is the variant ["Increment", int] | ["Decrement", int].

namespace C {
type storage = int;
const increment = (action: int, store: storage) : [list <operation>, storage] => [[], store + action];
const decrement = (action: int, store: storage) : [list <operation>, storage] => [[], store - action];
const testC = do {
let initial_storage = 42;
let orig = Test.originate(contract_of(C), initial_storage, 0tez);
let p : parameter_of C = Increment(1);
Test.transfer_exn(orig.addr, p, 1mutez);
return assert(Test.get_storage(orig.addr) == initial_storage + 1);

The special constructions contract_of(C) and parameter_of C are not first-class functions, they are special syntax which take a module or namespace name as a parameter. This means for example that some_function(contract_of) or contract_of(some_variable) are invalid uses of the syntax (a literal module or parameter name must always be passed as part of the syntax).