(¬; Alex's Stuff :¬)

mmmm ES6 pi = () => { value: 3,141592654 };

Sun, 13 Aug 2017 14:31:26 +0100

mmmm ES6

pi = () => { value: 3,141592654 };

Javascript: how to delete

Thu, 22 Jun 2017 12:07:06 +0100

Oh, what a lovely API:

'x/y/z'.replace(/\//g, '')
'xyz'

'x/y/z'.replace(/\//g)
'xundefinedyundefinedz'\

Manipulating browser history - a simple example

Fri, 30 Oct 2015 11:36:14 +0000

Manipulating browser history

Here’s a simple example of manipulating the browser history using javascript:

   <html>
            <head>
            </head>
            <body>

            <h1>
                    Counter: <span id="status"></span>
            </h1>
            <div id="controls">
                    <button id="next">Next</button>
            </controls>

            <script>
                    // capture BACK events
                    window.addEventListener('popstate', function(event) {
                            window.updateCounter(event.state.count);
                    });

                    window.updateCounter = function(count) {
                            window.count = count;
                            document.getElementById('status').innerHTML = count;
                    };
                    document.getElementById('next')
                            .addEventListener('click', function() {
                                    // create a fake history item
                                    var newCount = window.count + 1;
                                    window.history.pushState({ count: newCount }, '');
                                    window.updateCounter(newCount);
                            });

                    // set up initial state and fake history item
                    window.history.replaceState({ count: 0 }, '');
                    window.updateCounter(0);
            </script>

            </body>
    </html>

# Immutable Objects in Java Save some typing by declaring immutable object in Java like this: ...

Wed, 22 Jul 2015 15:32:20 +0100

# Immutable Objects in Java

Save some typing by declaring immutable object in Java like this:

public class SomeImmutableObject {
public final SomeClass field1;
public final SomeOtherClass field2;

public SomeImmutableObject(SomeClass value1, SomeOtherClass value2) {
field1 = value1;
field2 = value2;
}
}

Apparently in [Effective Java](http://uet.vnu.edu.vn/~chauttm/e-books/java/Effective.Java.2nd.Edition.May.2008.3000th.Release.pdf) [Joshua Bloch](https://en.wikipedia.org/wiki/Joshua_Bloch) wrote:

> While it’s never a good idea for a public class to expose fields directly, it is less harmful if the fields are immutable. You can’t change the representation of such a class without changing its API, and you can’t take auxiliary actions when a field is read, but you can enforce invariants.

and further

> In summary, public classes should never expose mutable fields. It is less harmful, though still questionable, for public classes to expose immutable fields.

I think it’s great to know when a class is immutable.

# Open NERDTree automatically To open [NERDTree][1] automatically when in the root directory of a...

Sat, 16 May 2015 16:26:11 +0100

# Open NERDTree automatically

To open [NERDTree][1] automatically when in the root directory of a project, add the following to your `.vimrc`:

if !empty(glob(“./.git/”))
autocmd VimEnter * NERDTree
autocmd VimEnter * wincmd p “ and move focus to the main window
endif

This assumes that you’re using [git][2] for version control, and [vim][3] :¬)

[1]: https://github.com/scrooloose/nerdtree
[2]: https://www.git-scm.com/
[3]: http://www.vim.org/

# StaleObjectException in grails domain custom validator Just ran into this issue where the custom...

Fri, 20 Sep 2013 13:11:00 +0100

# StaleObjectException in grails domain custom validator

Just ran into this issue where the custom validator in a Grails GORM domain object was throwing a `StaleObjectException` for no obvious reason. Turns out that referencing a transactional service in a custom validator will cause this exception to be thrown without fail.

## Fix?

Add the following to the top of your Service:

transactional = false

Painful.

# StackOverflowError from Grails Routing Plugin Was receiving the following rather confusing error...

Mon, 26 Aug 2013 13:56:22 +0100

# StackOverflowError from Grails Routing Plugin

Was receiving the following rather confusing error on startup of our grails app:

org.quartz.JobExecutionException: org.quartz.SchedulerException: Job threw an unhandled exception. [See nested exception: java.lang.reflect.UndeclaredThrowableException] [See nested exception: org.quartz.SchedulerException: Job threw an unhandled exception. [See nested exception: java.lang.reflect.UndeclaredThrowableException]]
at org.quartz.core.JobRunShell.run(JobRunShell.java:229)
at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:557)
Caused by: org.quartz.SchedulerException: Job threw an unhandled exception. [See nested exception: java.lang.reflect.UndeclaredThrowableException]
at org.quartz.core.JobRunShell.run(JobRunShell.java:224)
… 1 more
Caused by: java.lang.reflect.UndeclaredThrowableException
at grails.plugin.hibernatehijacker.template.HibernateTemplates.withTransaction(HibernateTemplates.groovy:37)
at grails.plugin.multitenant.core.MultiTenantService$_doWithTenantId_closure1.doCall(MultiTenantService.groovy:31)
at grails.plugin.hibernatehijacker.template.HibernateTemplates$_withNewSession_closure2.doCall(HibernateTemplates.groovy:65)
at grails.plugin.hibernatehijacker.template.HibernateTemplates.withNewSession(HibernateTemplates.groovy:57)
at grails.plugin.multitenant.core.MultiTenantService.doWithTenantId(MultiTenantService.groovy:30)
at grails.plugin.multitenantsingledbquartz2integration.TenantAwareJobFactory$1.execute(TenantAwareJobFactory.groovy:27)
at org.quartz.core.JobRunShell.run(JobRunShell.java:213)
… 1 more
Caused by: org.quartz.JobExecutionException: java.lang.StackOverflowError [See nested exception: java.lang.StackOverflowError]
at grails.plugin.quartz2.GrailsArtefactJob.execute(GrailsArtefactJob.java:66)
at grails.plugin.multitenantsingledbquartz2integration.TenantAwareJobFactory$_1_execute_closure1.doCall(TenantAwareJobFactory.groovy:28)
at grails.plugin.multitenant.core.MultiTenantService$_doWithTenantId_closure1_closure2.doCall(MultiTenantService.groovy:32)
at grails.plugin.hibernatehijacker.template.HibernateTemplates$_withTransaction_closure1.doCall(HibernateTemplates.groovy:39)
… 8 more
Caused by: java.lang.StackOverflowError
at RoutingGrailsPlugin$_initializeRouteBuilderHelpers_closure6.doCall(RoutingGrailsPlugin.groovy:113)
at RoutingGrailsPlugin$_initializeRouteBuilderHelpers_closure6.doCall(RoutingGrailsPlugin.groovy:113)
at RoutingGrailsPlugin$_initializeRouteBuilderHelpers_closure6.doCall(RoutingGrailsPlugin.groovy:113)
at RoutingGrailsPlugin$_initializeRouteBuilderHelpers_closure6.doCall(RoutingGrailsPlugin.groovy:113)
at RoutingGrailsPlugin$_initializeRouteBuilderHelpers_closure6.doCall(RoutingGrailsPlugin.groovy:113)
at RoutingGrailsPlugin$_initializeRouteBuilderHelpers_closure6.doCall(RoutingGrailsPlugin.groovy:113)

# The cause

Defining a camel route with `.process(new MyFakeProcessor())` where MyFakeProcessor *doesn’t* implement `org.apache.camel.Processor`.

# The fix

Replace

.process(new MyFakeProcessor())

With

.bean(new MyFakeProcessor(), ‘process’)

# simple, sensible bash logging This code will allow you to call e.g. `log ‘script...

Thu, 22 Aug 2013 09:32:00 +0100

# simple, sensible bash logging

This code will allow you to call e.g. `log ‘script starting…’` in a bash script, and formatted log output provided:

# [script_name] script starting…

Further, if a script is sourced from another script, logging in the parent script and child script will both acknowledge the parent, but will clearly show which script they are from:

# [parent_script] sourcing child…
# [parent_script] [child_script] script starting…

The code is below. It assumes the function will be included in a separate script file sourced from the main script.

function log {
local logStart=“#”
local sourceLen=${#BASH_SOURCE[@]}
# if including this function directly in the top-level
# script, terminating condition should be: `i>=0`
for ((i=$sourceLen-1; i>0; –i)); do
logStart=“$logStart [$(basename ${BASH_SOURCE[$i]})]”
done
echo “$logStart $@”
}

# Grails build-test-data plugin and compilation I had a strange experience recently where grails...

Thu, 22 Aug 2013 09:31:12 +0100

# Grails build-test-data plugin and compilation

I had a strange experience recently where grails unit and integration tests were happily passing on my machine (with `grails test-app unit:`), but failing on jenkins (with `grails clean; grails test-app unit:`). The error:

Failure: |
test_name(frontlinesms2.MySpec)
|
grails.buildtestdata.handler.ConstraintHandlerException: Validator constraint support not implemented in build-test-data, attempted value (0) does not pass validation: property amount of frontlinesms2.MyDomainClass
at grails.buildtestdata.handler.ValidatorConstraintHandler.handle(ValidatorConstraintHandler.groovy:14)
at grails.buildtestdata.DomainInstanceBuilder.createProperty_closure8(DomainInstanceBuilder.groovy:223)
at grails.buildtestdata.DomainInstanceBuilder.createProperty(DomainInstanceBuilder.groovy:219)
at grails.buildtestdata.DomainInstanceBuilder.createMissingProperty(DomainInstanceBuilder.groovy:210)
at grails.buildtestdata.DomainInstanceBuilder.populateInstance(DomainInstanceBuilder.groovy:168)
at grails.buildtestdata.DomainInstanceBuilder.build_closure5(DomainInstanceBuilder.groovy:145)
at grails.buildtestdata.DomainInstanceBuilder.logToGraph(DomainInstanceBuilder.groovy:332)
at grails.buildtestdata.DomainInstanceBuilder.build(DomainInstanceBuilder.groovy:144)
at grails.buildtestdata.DomainInstanceBuilder.build(DomainInstanceBuilder.groovy:143)
at grails.buildtestdata.BuildTestDataService.addBuildMethods_closure1(BuildTestDataService.groovy:22)
at frontlinesms2.MySpec.setup(MySpec.groovy:13)

What was weird about this was that I had explicitly set this value in `grails-app/conf/TestDataConfig.groovy` like so:

testDataConfig {
sampleData {
‘frontlinesms2.MyDomainClass’ {
amount = 1
}
}
}

Apparently this was ignored if `test-app` was called directly after a clean.

## How do you fix this?

grails clean
grails compile
grails test-app unit:

I.e. **add an explicit compile step**. I’m surprised this is necessary. But it is.

N.B. this occurred with grails 2.0.3 and java:

java version “1.6.0_27”
OpenJDK Runtime Environment (IcedTea6 1.12.6) (6b27-1.12.6-1ubuntu0.13.04.2)
OpenJDK 64-Bit Server VM (build 20.0-b12, mixed mode)

# WebDriver with a nice error message Currently we’re suffering from the following exception...

Wed, 27 Feb 2013 11:11:26 +0000

# WebDriver with a nice error message

Currently we’re suffering from the following exception quite regularly on our Jenkins server:

Build info: version: ‘2.30.0’, revision: 'dc1ef9ceb805a672f56dc49198f9ffbd4ca345c7’, time: '2013-02-19 09:14:38’
System info: os.name: 'Linux’, os.arch: 'amd64’, os.version: '3.2.0-37-generic’, java.version: '1.6.0_27’
Driver info: driver.version: FirefoxDriver
at org.openqa.selenium.firefox.internal.NewProfileExtensionConnection.start(NewProfileExtensionConnection.java:118)
at org.openqa.selenium.firefox.FirefoxDriver.startClient(FirefoxDriver.java:244)
at org.openqa.selenium.remote.RemoteWebDriver.(RemoteWebDriver.java:110)
at org.openqa.selenium.firefox.FirefoxDriver.(FirefoxDriver.java:188)
at org.openqa.selenium.firefox.FirefoxDriver.(FirefoxDriver.java:183)
at org.openqa.selenium.firefox.FirefoxDriver.(FirefoxDriver.java:179)
at org.openqa.selenium.firefox.FirefoxDriver.(FirefoxDriver.java:92)
at script1361962190832380912643.run_closure2(script1361962190832380912643.groovy:23)
at geb.driver.CallbackDriverFactory.getDriver(CallbackDriverFactory.groovy:29)
… 13 more
Caused by: org.openqa.selenium.firefox.NotConnectedException: Unable to connect to host 127.0.0.1 on port 7055 after 45000 ms. Firefox console output:
Maximum number of clients reachedMaximum number of clients reachedError: cannot open display: :93
Maximum number of clients reachedMaximum number of clients reachedError: cannot open display: :93

I *suspect* this is caused by either:

* new Firefox update not shutting down properly after Selenium tests are run; or
* manually terminated (killed) Jenkins builds not shutting down Firefox instances that were spawned as part of the job

## Solution?

log into server and `pkill firefox`. Ugly.

# Why are my Grails functional tests slow? ## Database flushes slow down over time I’ve...

Wed, 27 Feb 2013 08:02:00 +0000

# Why are my Grails functional tests slow?

## Database flushes slow down over time

I’ve posted this to the Grails mailing list - hopefully we’ll get some ideas from there: [“Flushes get slower in later tests (integration, functional)”](http://grails.1312388.n4.nabble.com/Flushes-get-slower-in-later-tests-integration-functional-td4641847.html)

Combine this fact with Spock Specifications like this:

class MySpec extends spock.lang.Specification {
setup() {
100.times {
new DomainObject().save(flush:true)
}
}
}

…and you get a very slow test suite. This should also slow down integration tests :¬)

## Geb selecters are very slow for big content

It may seem clever to write Geb selecters like

messages { moduleList MessageListRow, $(‘tbody tr’) }

and then call them like this:

messages[0].select.click()

Actually it’s not very clever at all - it’s very very slow. This is because, I think, Selenium individually loads each `MessageListRow` using a separate network request. Even with 50 `MessageListRow`s, it becomes painfully slow to do a simple thing. To get decent performance, refactor like so:

message { index -> ++index; $(“tbody tr:nth-child($index)”) }
toggleSelect { index -> message(index).find('input[type=checkbox]’).click(); true }
…
toggleSelect(0)

## Anything else?

Probably, but even just a couple of tweaks to work around the problems above cut our full test suite execution time from 65 to 45 minutes.

# Jenkins jobs/ directory permissions problems Sometimes our Jenkins user loses access to the...

Fri, 22 Feb 2013 06:56:42 +0000

# Jenkins jobs/ directory permissions problems

Sometimes our Jenkins user loses access to the `jobs` directory when our server is restarted. We’ve not found the cause yet, but the simplest fix seems to be:

sudo chmod -R jenkins:jenkins /var/lib/jenkins; sudo su - jenkins; chmod +x jobs

# Spock specs and grails integration tests Earlier today I started getting the following strange...

Wed, 13 Feb 2013 14:06:58 +0000

# Spock specs and grails integration tests

Earlier today I started getting the following strange error in an integration test for a grails app:

| java.lang.IllegalStateException: No thread-bound request found: Are you referring to request attributes outside of an actual web request, or processing a request outside of the originally receiving thread? If you are actually operating within a web request and still receive this message, your code is probably running outside of DispatcherServlet/DispatcherPortlet: In this case, use RequestContextListener or RequestContextFilter to expose the current request.
at frontlinesms2.controller.AppInfoControllerISpec.appInfoService should be called with request for relevant data(AppInfoControllerISpec.groovy:20)
| Completed 1 spock test, 1 failed in 252ms

The offending code:

given:
controller.request.JSON = x

The problem? I had mistakenly extended `spock.lang.Specification` instead of `grails.plugin.spock.IntegrationSpec`. Oops.

# findAllByXNotInList throws NullPointerException with empty list I guess this is a bug (grails...

Wed, 06 Feb 2013 12:45:00 +0000

# findAllByXNotInList throws NullPointerException with empty list

I guess this is a bug (grails 2.0.3, h2 database):

DomainClass.findAllByIdInList([]) returns ok, but DomainClass.findAllByIdNotInList([]) throws a NullPointerException:

groovy:000> weirdfinder.Dom.findAllByIdInList([])
===> []
groovy:000> weirdfinder.Dom.findAllByIdNotInList([])
ERROR java.lang.NullPointerException:
null
at org.hibernate.loader.criteria.CriteriaQueryTranslator.getQueryParameters (CriteriaQueryTranslator.java:316)
at org.hibernate.loader.criteria.CriteriaLoader.list (CriteriaLoader.java:119)
at org.hibernate.impl.SessionImpl.list (SessionImpl.java:1716)
at org.hibernate.impl.CriteriaImpl.list (CriteriaImpl.java:347)
at org.springframework.orm.hibernate3.HibernateTemplate.doExecute (HibernateTemplate.java:406)
at org.springframework.orm.hibernate3.HibernateTemplate.executeFind (HibernateTemplate.java:343)
at org.grails.datastore.gorm.GormStaticApi$_methodMissing_closure2.doCall (GormStaticApi.groovy:105)
at org.grails.datastore.gorm.GormStaticApi$_methodMissing_closure2.call (GormStaticApi.groovy)
at groovysh_evaluate.run (groovysh_evaluate:2)
…
groovy:000> weirdfinder.Dom.findAllByIdNotInList([1L])
===> []

or is this a feature?

For added fun, passing an integer in the list throws a ClassCastException:

groovy:000> weirdfinder.Dom.findAllByIdNotInList([1])
ERROR java.lang.ClassCastException:
java.lang.Integer cannot be cast to java.lang.Long
at org.hibernate.type.descriptor.java.LongTypeDescriptor.unwrap (LongTypeDescriptor.java:36)

The domain class was:

package weirdfinder

class Dom {
String text
}

Also tested on: Grails 2.0.4.

I guess this has been fixed as Grails 2.2.0 gives different inconsistent results - sometimes an empty list, and sometimes nothing at all:

groovy:000> weirdfinder.Dom.findAllByIdInList([])
===> []
groovy:000> weirdfinder.Dom.findAllByIdInList([1])
groovy:000> weirdfinder.Dom.findAllByIdInList([1L])
===> []
groovy:000> weirdfinder.Dom.findAllByIdNotInList([])
groovy:000> weirdfinder.Dom.findAllByIdNotInList([1])
groovy:000> weirdfinder.Dom.findAllByIdNotInList([1L])
===> []

# Jenkins Violations with JSLint From what I’ve seen, getting Jenkins Violations plugin to...

Fri, 19 Oct 2012 07:36:00 +0100

# Jenkins Violations with JSLint

From what I’ve seen, getting Jenkins Violations plugin to work with JSLint requires using [jslint4java][1] to generate the jslint report as XML.

The closest I could find to a spec for the generated XML was looking at the [JSLintParser implementation][2] and [unit tests][3]. It looks like this:

From this, it’s fairly simple to make a script which converts JSLint’s JSON output (`jslint –json`) into the XML format required by jenkins-violations-plugin.

[1]: https://code.google.com/p/jslint4java/
[2]: https://github.com/jenkinsci/violations-plugin/blob/master/src/main/java/hudson/plugins/violations/types/jslint/JsLintParser.java
[3]: https://github.com/jenkinsci/violations-plugin/blob/master/src/test/java/hudson/plugins/violations/types/jslint/JsLintParserTest.java

# Groovy’s `String.tokenize()` vs. Java’s `String.split()` Re-discovered a little...

Wed, 17 Oct 2012 12:38:00 +0100

# Groovy’s `String.tokenize()` vs. Java’s `String.split()`

Re-discovered a little difference between Groovy’s `String.split()` and `String.tokenize()` methods today:

‘abc.123.wtf’.split(’.’) == []
'abc.123.wtf’.tokenize(’.’) == ['abc’, '123’, 'wtf’]

because…

> [String.split()](http://docs.oracle.com/javase/6/docs/api/java/lang/String.html#split%28java.lang.String%29)
> Splits this string around matches of the given regular expression.

vs.

> [String.tokenize()](http://groovy.codehaus.org/groovy-jdk/java/lang/String.html#tokenize%28java.lang.String%29)
> Tokenize a String based on the given string delimiter.

Why anyone would ever want to call `String.split(’.’)` is anybody’s guess.

# Fixing Git alias jit=`which git` && alias git=“echo No command...

Fri, 12 Oct 2012 09:13:20 +0100

# Fixing Git

alias jit=`which git` && alias git=“echo No command ‘git’ found, did you mean: jit”

# Grails Heroku mystery issue Currently seeing: ## Error 500: Internal Server Error ### URI ...

Wed, 29 Aug 2012 22:03:03 +0100

# Grails Heroku mystery issue

Currently seeing:

## Error 500: Internal Server Error

### URI
/
### Class
java.lang.IllegalStateException
### Message
WRITER

### Trace

Line | Method
->> 627 | getOutputStream in org.eclipse.jetty.server.Response
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| 1330 | doFilter in org.eclipse.jetty.servlet.ServletHandler$CachedChain
| 51 | doFilterInternal in grails.plugin.databasesession.SessionProxyFilter
| 1330 | doFilter in org.eclipse.jetty.servlet.ServletHandler$CachedChain
| 478 | doHandle … . in org.eclipse.jetty.servlet.ServletHandler
| 119 | handle in org.eclipse.jetty.server.handler.ScopedHandler
| 520 | handle … . . in org.eclipse.jetty.security.SecurityHandler
| 227 | doHandle in org.eclipse.jetty.server.session.SessionHandler
| 941 | doHandle … . in org.eclipse.jetty.server.handler.ContextHandler
| 409 | doScope in org.eclipse.jetty.servlet.ServletHandler
| 186 | doScope … . in org.eclipse.jetty.server.session.SessionHandler
| 875 | doScope in org.eclipse.jetty.server.handler.ContextHandler
| 117 | handle … . . in org.eclipse.jetty.server.handler.ScopedHandler
| 250 | handle in org.eclipse.jetty.server.handler.ContextHandlerCollection
| 149 | handle … . . in org.eclipse.jetty.server.handler.HandlerCollection
| 110 | handle in org.eclipse.jetty.server.handler.HandlerWrapper
| 345 | handle … . . in org.eclipse.jetty.server.Server
| 441 | handleRequest in org.eclipse.jetty.server.HttpConnection
| 919 | headerComplete . in org.eclipse.jetty.server.HttpConnection$RequestHandler
| 582 | parseNext in org.eclipse.jetty.http.HttpParser
| 218 | parseAvailable . in “
| 51 | handle in org.eclipse.jetty.server.AsyncHttpConnection
| 586 | handle … . . in org.eclipse.jetty.io.nio.SelectChannelEndPoint
| 44 | run in org.eclipse.jetty.io.nio.SelectChannelEndPoint$1
| 598 | runJob … . . in org.eclipse.jetty.util.thread.QueuedThreadPool
| 533 | run in org.eclipse.jetty.util.thread.QueuedThreadPool$3
^ 636 | run … … in java.lang.Thread

Hopefully I’ll find out why tomorrow!

# Git clone gets stuck when “Receiving objects” Setting up our Jenkins machine...

Wed, 25 Jul 2012 13:36:00 +0100

# Git clone gets stuck when “Receiving objects”

Setting up our Jenkins machine recently, and with Zuku internet being very patchy, I found git constantly getting stuck while trying to clone.

Cloning into ’/var/lib/jenkins/jobs/frontlinesms2-core-maintenance-service/workspace’…
remote: Counting objects: 51274, done.
remote: Compressing objects: 100% (12986/12986), done.
Receiving objects: 2% (1026/51274), 196.00 KiB Kib/s

It seems that [git doesn’t work very well with poor internet connections](http://stackoverflow.com/questions/3954852/how-to-complete-a-git-clone-for-a-big-project-on-an-unstable-connection). This is a shame, and there are only two suggested solutions:

## 1. download as a folder using e.g. wget
I’m not sure how practical this is in real life - e.g. if you’re downloading a folder from github or an Apache project, is it actually possible to wget a git repo?

## 2. shallow clone
Add the argument `–depth=1` to the arguments of `git clone`, e.g.

git clone –depth=1 git://username@example.com

This still suffers, though, from the standard issues of having a poor connection - it just has a higher chance of successfully completing before the connection is interrupted.

# Adding display support for Jenkins on Ubuntu Running Selenium tests on our new Jenkins server was...

Wed, 25 Jul 2012 13:15:00 +0100

# Adding display support for Jenkins on Ubuntu

Running Selenium tests on our new Jenkins server was failing with:

Error: no display specified

Turns out we need to configure a display for the Jenkins user. I couldn’t find any clear information on the best way to do this, but the following seems to work:

## Start Xvfb

Add the following to `/etc/init/jenkins.conf`:

pre-start script # this line was already here
# Start X graphics so that Firefox can run from Jenkins functional tests
Xvfb :93 -ac &
# Completed X setup
…
end script

I chose the number _93_ because it’s quite big and doesn’t clash with other configured displays on my system.

## Set DISPLAY environment variable

In Jenkins configuration, set the environment variable `DISPLAY` to `:93`.