I have this parameter for a function:

type modify_list is 
| Add of list(address)
| Remove of list(address)

type modify_list_michelson is michelson_or_right_comb(modify_list)

When I try to supply the parameter in my truffle tests like this:

{ add: [account1, account2], remove: [] }

I get this error:

Received 1 arguments while expecting one of the following signatures ([["add","list"],["remove","list"]])

Can anyone tell me how to supply the arguments correctly? I've tried simplifying the parameter with addresses instead of a list and tried pretty much every data structure I could think of in the JS test, but no success yet.

  • Do you have a deployed contract for that? I'd like to run some tests against it. Oct 27, 2020 at 13:15

2 Answers 2


The correct syntax for the parameter is the following: "remove", [account1, account2] (2 different parameters, no object).
I built a simple contract to emulate your case, deployed it and wrote a little script to test it. After calling the entrypoint of your choice, you must provide 2 parameters: 1- the field you want to set the union value with 2- its parameters (if any).
Let me know if you have other questions :)


I believe the error is that you pass the 2 parameters (add and remove), but you should only pass the chosen one. I suggest you try : { add: [account1, account2] }

  • 1
    I tried that, unfortunately I got the same error as well Oct 23, 2020 at 20:53

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