child

properties([
    parameters([
        string(name: 'DEPLOY_TEXT', defaultValue: 'defVal', description: '')
    ])
])
echo "direct value: ${DEPLOY_TEXT}"
echo "param value: ${params.DEPLOY_TEXT}"
if(DEPLOY_TEXT == 'justin') {
    currentBuild.result = 'FAILURE'
}

parent

stage 'downstream'
def job = build job: "../jenkins-test/args-p", parameters: [
    string(name: 'DEPLOY_TEXT', value: 'from parent!')
]
echo "Job Result: ${job.getResult()} - ${job.getAbsoluteUrl()}"