
You can spoof an account by providing the caller address to the invoke function like this:



```
await contract.function(
    arg1=felt,
    arg2=felt2,
).invoke(caller_address=private_to_stark_key(123))

```

If you want a more detailed example of how the python unit testing framework works you can check these 2 links


<https://github.com/starknet-edu/basecamp/blob/main/camp_4/buidl/tests/test_contract.py>
<https://github.com/starknet-edu/starknet-debug/tree/master/python>



ㅤ
_This answer was originally posted on [Stack Overflow](https://stackoverflow.com/questions/73034919/testing-starknet-cairo-contract-function-with-address)_


I built a module with Cairo language and I would like to unit test it. The contract is pretty simple : it manages a list of authorized addresses and provide some "modifier" functions to help.


I have taken the sample unit testing code from the documentation but nothing is referring about sending an account address to a function with python.


How should I proceed ?


Thanks in advance



ㅤ
_This question was originally posted on [Stack Overflow](https://stackoverflow.com/questions/73034919/testing-starknet-cairo-contract-function-with-address)_

Testing Starknet Cairo contract function with address

Hey,
As each storage value is by default initialized to 0, does writing it to zero actually do something? Does it use storage in layer 1 with value 0? Or does it just do nothing?
Should I check that the value I want to write is different than 0 before writing it otherwise I will waste storage?

The same idea: does writing a storage value to 0 free storage on l1

Does writing it to zero actually do something?

Is there any blockchain project contract supporting web2 scripts executable on VIa EVM?

I think it only one Tru (truebit)

Is there any blockchain project contract supporting web2 scripts executable on VIa EVM?

Why am I getting an `account __execute__` error message `ape_starknet.exceptions.StarknetProviderError: Can only send invoke transaction to an account execute method`?


ApeWorX: Why am I getting an "account __execute__" error message?

Hello! This is day 10 of the 17 days of the Cairo Challenge. And I have no idea how to solve the [playground](https://www.cairo-lang.org/playground/) exercise “Bitwise operations”.  Perhaps you can help me?

```
// The bitwise builtin allows you to perform bitwise operations
// (and, or, xor) on integers up to 251 bits.
//
// The following code implements the function xor_last_hex_digits,
// which takes the two last hexadecimal digits and "xor"s them.
// For example, in 0x1234 the last two digits are 3 and 4,
// and their xor is 3^4=7.
//
// Fix the missing code and make sure it works.

%builtins bitwise

from starkware.cairo.common.bitwise import bitwise_and, bitwise_xor
from starkware.cairo.common.cairo_builtins import BitwiseBuiltin

// Returns the xor of the last two hexadecimal digits.
func xor_last_hex_digits{bitwise_ptr: BitwiseBuiltin*}(x: felt) -> (res: felt) {
    // Fix and uncomment the line below.
    // let (digit0) = ...

    let (shifted_digit1) = bitwise_and(x, 0xF0);
    tempvar digit1 = shifted_digit1 / 0x10;

    return bitwise_xor(digit0, digit1);
}

func main{bitwise_ptr: BitwiseBuiltin*}() {
    let (res) = xor_last_hex_digits(0x1234);
    assert res = 7;

    return ();
}
```

---

> Answers to this question are a part of the ✨ 17 days of Cairo Lang with Playground & Newton. ✨
> 

*Vote for your favorite answer - the best answer will win a $10 award. A new day – a new reward! During the next 17 days, our goal is to attract more developers to the Cairo language and to systematize the knowledge of Cairo lang. [Read rules](https://www.notion.so/17-days-of-Cairo-Lang-with-Newton-550dfcda6a2d449ca468be293c776578)*

How to make Bitwise operations in Cairo Lang using %builtins bitwise, bitwise_xor?

hi,guys

QUESTION, where can i get test tokens?

_This question was originally posted on [StarkNet Discord](https://www.newton.so/view?tags=discord)_

Where can i get test tokens in StarkNet?

What are advantages of Cairo (vs Solidity) for Starknet?


ㅤ
_This question was originally posted on [Triality](https://triality.org/question/231)_

Cairo v. Solidity


As I understand it, `let` defines a reference, which can be seen as an alias, so for example `let x = y * y * y` doesn't compute `y * y * y` but the occurrences of `x` will be replaced by `y * y * y`.
Local variables are similar to other languages local variables.


As in <https://www.cairo-lang.org/docs/hello_cairo/dict.html>, what does it mean to write `let (local dict_start : DictAccess*) = alloc()`? That every instance of `local dict_start : DictAccess*` will be replaced by `alloc()`? Why not just `local (dict_start : DictAccess*) = alloc()` or `let (dict_start : DictAccess*) = alloc()`?



ㅤ
_This question was originally posted on [Stack Overflow](https://stackoverflow.com/questions/71738301/what-does-it-mean-to-declare-a-local-variable-inside-a-let)_

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