Create "leaf" job with a single upstream dependency "before_leaf" where "before_leaf" has many (in this case 40) upstream dependencies.

gistfile1.groovy

job_prefix = 'jenkins21605_caseA_'

println 'Deleting jobs from previous tests...'
for (p in Jenkins.instance.allItems) {
    if (!p.name.startsWith(job_prefix)) continue
    println '- ' + p.name
    p.delete()
}
println ''

def createProject(job_name, upstream_names) {
    job_config_template = '''
<project>
  <actions/>
  <description></description>
  <keepDependencies>false</keepDependencies>
  <properties/>
  <scm class="hudson.scm.NullSCM"/>
  <assignedNode>master</assignedNode>
  <canRoam>false</canRoam>
  <disabled>false</disabled>
  <blockBuildWhenDownstreamBuilding>false</blockBuildWhenDownstreamBuilding>
  <blockBuildWhenUpstreamBuilding>true</blockBuildWhenUpstreamBuilding>
  <triggers>
    <jenkins.triggers.ReverseBuildTrigger>
      <spec></spec>
      <upstreamProjects>%1$s</upstreamProjects>
      <threshold>
        <name>UNSTABLE</name>
        <ordinal>1</ordinal>
        <color>YELLOW</color>
        <completeBuild>true</completeBuild>
      </threshold>
    </jenkins.triggers.ReverseBuildTrigger>
  </triggers>
  <concurrentBuild>false</concurrentBuild>
  <builders>
    <hudson.plugins.groovy.SystemGroovy plugin="groovy@1.24">
      <scriptSource class="hudson.plugins.groovy.StringScriptSource">
        <command>println &apos;dummy build step&apos;</command>
      </scriptSource>
      <bindings></bindings>
      <classpath></classpath>
    </hudson.plugins.groovy.SystemGroovy>
  </builders>
  <publishers/>
  <buildWrappers/>
</project>
'''
    upstream_projects = ''
    for (upstream_name in upstream_names) {
        upstream_projects += job_prefix + upstream_name + ','
    }
    job_config = sprintf(job_config_template, upstream_projects)
    stream = new StringBufferInputStream(job_config)
    println '- ' + job_prefix + job_name
    Jenkins.instance.createProjectFromXML(job_prefix + job_name, stream)
}

def createProjects(parent_name, count) {
    range = 1..count
    for (i in range) {
        createProject(parent_name + String.format("%0" + 2 + "d", i), [parent_name])
    }
}

println 'Creating new job hierarchy...'
createProject('', [])
all_parents = []
range = 1..40
parent = ''
for (i in range) {
    name = String.format("%0" + 2 + "d", i)
    createProject(name, [parent])
    parent = name
    all_parents += [parent]
    println all_parents
}
createProject('before_leaf', all_parents)
createProject('leaf', ['before_leaf'])
println ''

println 'You can create a view to show all test jobs using the regular expression: ' + job_prefix
println ''

println 'Please trigger the root job: ' + job_prefix
println 'And then look at the leaf job: ' + job_prefix + 'leaf'