remix-project/remix-tests/tests/various_sender/sender_test.sol

import "remix_tests.sol"; // this import is automatically injected by Remix.
import "remix_accounts.sol";

contract SenderTest {
   
    function beforeAll () {}
    
    /// 1
    function checkSenderIs1 () public {
        Assert.equal(msg.sender, TestsAccounts.getAccount(1), "wrong sender in checkSenderIs1");
    }
    
    /// 0
    function checkSenderIs0 () public {
        Assert.equal(msg.sender, TestsAccounts.getAccount(0), "wrong sender in checkSenderIs0");
    }

    /// 1
    function checkSenderIsNt0 () public {
        Assert.notEqual(msg.sender, TestsAccounts.getAccount(0), "wrong sender in checkSenderIsNot0");
    }

    /// 2
    function checkSenderIsnt2 () public {
        Assert.notEqual(msg.sender, TestsAccounts.getAccount(1), "wrong sender in checkSenderIsnt2");
    }
}