Changed Code 3

function testCmd1(p: player):
    open virtual chest with 2 rows named "&4Test" to {_p}
    format gui slot 0 of player with diamond named "Test Cmd" to run {_p} command "/testcmd12"
command /testcmd12:
    trigger:
        wait 1 tick
        message "Test Worked"

function testCmd1(p: player):
    open virtual chest with 2 rows named "&4Test" to {_p}
    format gui slot 0 of {_p} with diamond named "Test Cmd" to run player command "/testcmd12"
command /testcmd12:
    trigger:
        wait 1 tick
        message "Test Worked"

function testCmd1(p: player):
    open virtual chest with 2 rows named "&4Test" to {_p}
    format gui slot 0 of player with diamond named "Test Cmd" to run player command "/testcmd12"
command /testcmd12:
    trigger:
        wait 1 tick
        message "Test Worked"