How to use Jenkins declarative pipeline to build and test on multiple platforms

1. post{} block should only follow steps{} or parallel{} (for parallel stages) to take effect.

2. If you require post to be executed in a node environment, you should provide a node to the entire stage (agent{} statement).

You could try to use parallel stages execution. Also I'd suggest to use functions to shorten the code.

Something like this:

void Clean() {    dir("build") {        deleteDir()        writeFile file:'dummy', text:'' // Creates the directory    }}void SmthElse(def optionalParams) {    // some actions here}pipeline {    agent none    options {        skipDefaultCheckout(true)   // to avoid force checkouts on every node in a first stage        disableConcurrentBuilds()   // to avoid concurrent builds on same nodes    }    stages {        stage('Clean') {            failfast false            parallel {                    stage('Linux') {                        agent {label 'linux'}                        steps {Clean()}                        post {                            // post statements for 'linux' node                            SmthElse(someParameter)                        }                    }                    stage('Windows') {                        agent {label 'windows'}                        steps {Clean()}                        post {                            // post statements for 'windows' node                        }                    }                    stage('MacOS') {                        agent {label 'mac'}                        steps {Clean()}                        post {                            // post statements for 'mac' node                        }                    }            }            post {                // Post statements OUTSIDE of nodes (i.e. send e-mail of a stage completion)            }        }        // other stages (Build/Test/Etc.)    }}

Alternatively you can use node in post statements:

stage('Test') {    steps {        // your parallel Test steps    }    post {        always {            script {                parallel (                    "linux" : {                        node('linux') {                            // 'linux' node post steps                        }                    },                    "windows" : {                        node('windows') {                            // 'windows' node post steps                        }                    }                    // etc                )            }        }    }}