ReceiveTest.sol

pragma solidity 0.6.4;

/**
 * @title ReceiveTest
 * @author Shane Fontaine - <shane6fontaine@gmail.com>
 * @notice THIS IS UNAUDITED CODE. DO NOT USE IN PRODUCTION. USE AT YOUR OWN RISK.
 * @dev Testing Solidity 0.6.x receive() function
 */



contract ReceiveTest {
    uint256 public a = 0;
    uint256 public b = 0;
    
    receive () external payable {
        // Will fail if `send()` or `transfer()`
        a = 1;
        b = 1;
    }
    
    function getBalance() external view returns (uint256) {
        return address(this).balance;
    }

}

contract SendTest {
    function myTest(address payable _receiveAddress) external payable {
        _receiveAddress.transfer(msg.value);
    }
}

have you solved this problem?

I don't understand - I read that if the contract had a receive function then it would get called if a .send or .transfer is made to the recipient contract ?

In this code it says that it the receive() function will fail 'if send() or transfer()' - why is that?

@shanefontaine @elferno

It's because transfer and send have 23000 gas fixed https://solidity-by-example.org/sending-ether/