Cannot transition to another status in Jira Custom script post-function - jira

Question

I am using a Custom script post-function [ScriptRunner] that is triggered after clicking on the transition "MounaCompleted" located in my menu item (last item in the menu).
I am using the following code to transition an issue after clicking on the "Completed" menu item.
Initially, my issue is in the status "Open" and I would like to transition my issue from "Open" to "Fixed". I am using the following code which does not work. My problem  is that 
if (validationResult.isValid())
 evaluates to false and I end up printing 
Failed to transition subtask 7 com.atlassian.jira.bc.issue.IssueService$TransitionValidationResult#105aff4d
import com.atlassian.jira.issue.Issue;
import com.atlassian.jira.workflow.WorkflowManager
import org.apache.log4j.Logger
import com.atlassian.jira.component.ComponentAccessor
def log = Logger.getLogger("atlassian-jira.log")
log.warn("This is the last action ")
WorkflowManager workflowManager = ComponentAccessor.getWorkflowManager();
def issueService = ComponentAccessor.getIssueService()
def user = ComponentAccessor.getJiraAuthenticationContext().getLoggedInUser()
    if (issue.status.name == "Open") {
     log.warn("Failed to transition subtask 1"+issue.status.name)
        def issueInputParameters = issueService.newIssueInputParameters()
        issueInputParameters.with {
            log.warn("Failed to transition subtask 2")
            setResolutionId("10001") // resolution of "Fixed"
            setComment("*Resolving* as a result of the *Resolve* action being applied to the parent.")
            setSkipScreenCheck(true)
        }
        // validate and transition subtask
                    log.warn("Failed to transition subtask 10 "+ user+" "+ issue.getId()+" "+ 10001+" "+ issueInputParameters)
   
     def validationResult = null
    try{
         validationResult = issueService.validateTransition(user, issue.getId(), 10001, issueInputParameters)
    }
    catch(Exception e){
    log.warn("Failed to transition subtask 3 "+e)
    }
       
        if (validationResult.isValid()) {
            def issueResult = issueService.transition(user, validationResult)
            log.warn("Failed to transition subtask 4")
            if (!issueResult.isValid()) {
            log.warn("Failed to transition subtask 5")
                log.warn("Failed to transition subtask ${issue.getId()}, errors: ${issueResult.errorCollection}")
            }else{
                     log.warn("Failed to transition subtask 6")
                     log.warn("success")
            }
        } else {
                 log.warn("Failed to transition subtask 7 "+validationResult)
            log.warn("Could not transition subtask ${issue.getId()}, errors: ${validationResult.errorCollection}")
        }
    }else {
                    log.warn("Failed to transition subtask 8")
                    log.warn("Failed to transition subtask ")
            log.warn("Failed to transition subtask3333 "+issue.getId())
    }

Answer 1

import com.atlassian.jira.user.ApplicationUser
import com.atlassian.jira.issue.MutableIssue;
import com.atlassian.jira.issue.Issue;
import java.util.HashMap;
import java.util.List;
import com.atlassian.jira.component.ComponentAccessor;
import com.atlassian.jira.issue.Issue;
import com.atlassian.jira.workflow.JiraWorkflow
import com.atlassian.jira.workflow.WorkflowManager
import org.apache.log4j.Logger
import com.atlassian.jira.component.ComponentAccessor
import com.atlassian.jira.issue.changehistory.ChangeHistoryItem
import com.atlassian.jira.bc.issue.IssueService
import com.atlassian.jira.issue.IssueInputParametersImpl
import com.atlassian.jira.bc.issue.IssueService.IssueValidationResult
import com.atlassian.jira.user.ApplicationUser
import com.opensymphony.module.propertyset.PropertySet;
import com.opensymphony.workflow.WorkflowException;
import com.opensymphony.workflow.loader.ActionDescriptor;
import com.opensymphony.workflow.loader.StepDescriptor;
import com.opensymphony.workflow.spi.SimpleStep;
import com.atlassian.jira.component.ComponentAccessor
import com.atlassian.jira.config.ConstantsManager
def log = Logger.getLogger("atlassian-jira.log")
if (issue.getStatus().getSimpleStatus().getId().equals("1")) {
log.warn("MOUNA 1");
int transitionFromOpentoFixed = 71;
int transitionFromFixedToTested = 111;
int transitionFromTestedToCompleted = 131;
log.warn("MOUNA 100 transitionFromOpentoFixed " + issue.getStatus());
transition(transitionFromOpentoFixed, "Fixed");
log.warn("MOUNA 101 transitionFromFixedToTested " + issue.getStatus());
transition(transitionFromFixedToTested, "Tested");
log.warn("MOUNA 102 transitionFromTestedToCompleted " + issue.getStatus());
transition(transitionFromTestedToCompleted, "Completed");
}
void transition(int transitionToBeDone, String destinationStatus) {
issue = ComponentAccessor.getIssueManager().getIssueObject(issue.id)
def currentUser = ComponentAccessor.getJiraAuthenticationContext().getLoggedInUser()
log.warn("MOUNA 5 STATUS " + issue.getStatus());
log.warn("MOUNA 6 ");
String issueKey = issue.getKey()
log.warn("MOUNA 7 ");
IssueService issueService = ComponentAccessor.getIssueService()
log.warn("MOUNA 8");
log.warn("MOUNA 9 ");
def issueInputParameters = issueService.newIssueInputParameters()
issueInputParameters.setComment("Transitioning issue from status "+ issue.getStatus().getName()+" to status "+ destinationStatus );
transitionValidationResult = issueService.validateTransition(currentUser, issue.id, transitionToBeDone, issueInputParameters)
log.warn("MOUNA 10");
if (transitionValidationResult.isValid()) {
log.warn("MOUNA 11 transition is valid");
def transitionResult = issueService.transition(currentUser, transitionValidationResult)
log.warn("MOUNA 12 ");
if (transitionResult.isValid()) {
log.warn("MOUNA 13 " + issue.getStatus());
} else {
log.warn("MOUNA 14 transitionResult not valid");
}
}
}