If the mandatory filed is empty, we should block the "Build" button or give the information to end user clearly.

So far, we defined conditions in the pipeline stage as below. We could find the error after the building.

But we hope to block the "Build" button and give the clear info to user quickly before starting the build.

stage('preparation') {            
steps {                
script {                    
if (test.isEmpty()) {                        
error("No test available. Terminating build.")                    
}