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How to convert Postman API test into JMeter load test

Posman_meets_JMeter

While working on mobile application API tests we were thinking how to use the same test set for functional tests as well as for load test and stress test. This would be useful as application was rapidly changing and having separate test set for functional and load/stress test was a trouble. As it would require to double efforts for maintaining this test and keep them up to date.

As I already said in one of my previous posts, I am a bit lazy when it comes to manual work. So I pushed an idea to spend a bit more time for the first time and create a converted that will allow you to give Postman environment and tests as input and get jmx file for JMeter as output. This is what I plan to talk about in current post.

So lets start. As usually I will share some code and explain our approach step by step. A link to a script will be at the end of this post.

  • Step 1. Decide which gems will be used. We started with Nokogiri and URI
  • Step 2. Parse input files. In order to properly work with different environments on Postman side we need to have at least two file as input. Environment file with variables for current environment and tests file. Also we need a file name to output result to. It looks like this in our case:
    [code lang="ruby"]
#!/bin/ruby
require 'json'
require 'nokogiri'
require 'uri'
# Parse args
postman_file = nil
postman_env_file = nil
jmeter_file = nil
out_file = nil
ARGV.each do|a|
arg = a.split('=')
if arg[0] == '--postman_file'
postman_file = arg[1].strip
puts "Postman tests file: #{arg[1]}"
end
if arg[0] == '--postman_env_file'
postman_env_file = arg[1].strip
puts "Postman environment file: #{arg[1]}"
end
if arg[0] == '--out_file'
out_file = arg[1].strip
puts "Postman ouput file: #{arg[1]}"
end
end
if postman_file.nil?
p "--postman_file is not set"
exit
end
if postman_env_file.nil?
p "--postman_env_file is not set"
exit
end
begin
postman_file = File.read(postman_file)
rescue
p "File #{postman_file} is not found. Make sure you set a correct path"
end
begin
postman_env_file = File.read(postman_env_file)
rescue
p "File #{postman_env_file} is not found. Make sure you set a correct path"
end
test_hash = nil
env_hash = nil
begin
test_hash = JSON.parse(postman_file)
rescue
p "Cannot parse #{postman_file} as json file"
end
begin
env_hash = JSON.parse(postman_env_file)
rescue
p "Cannot parse #{postman_file} as json file"
end
[/code]
  • Step 3. Now when we validated input files and parsed them, time to generate a file a single file that will have tests with variables replaced. So we can use tests with actual values to generate thread group and threads for JMeter.
    [code lang="ruby"]
def collect_vars arr
result = []
arr.select{|el| el.match(/postman.setEnvironmentVariable/)}.each do |var|
set = var.split("(")[1].split(",")
page_values = set[1].gsub(/\);/,'').split('[').select{|e| !e.gsub!("]","").nil?}.map{|d| d.gsub("'","")}
result.push({:var_name=>JSON.parse(set[0]), :page_value=>{:element => page_values.last, :index => page_values[-1].match(/d+/) ? page_values[-1] : 0}})
end
result.empty? ? nil : result
end
def generate_json_with_var postman_file, postman_env_file
begin
env_hash = JSON.parse(postman_env_file)
rescue
p "Cannot parse #{postman_file} as json file"
end
variables = {}
env_hash["values"].collect{|element| variables[element["key"]] = element["value"] }
variables.each do |key, value|
postman_file.gsub!(/\{\{#{key}\}\}/, value)
end
begin
test_hash = JSON.parse(postman_file)
rescue
p "Cannot parse #{postman_file} as json file"
end
test_hash
end
def collect_requests input
res = []
input['item'].each do |i|
i["item"].each do |test|
vars = collect_vars test["event"].first["script"]["exec"] if test["event"]
test["request"]["vars"] = vars if !vars.nil?
res.push(test["request"])
end
end
res
end
test_hash = generate_json_with_var postman_file, postman_env_file
requests = collect_requests test_hash
[/code]
    • Step 4. As we have a data for each request we need to generate a new jmx file with xml structure for ThreadGroup and RegexExtractor that will create variables in JMeter to make sure that tests will be dynamic and if they written properly, they will remove data after test was completed.
      [code lang="ruby"]
builder = Nokogiri::XML::Builder.new do |xml|
xml.jmeterTestPlan("version"=>"1.2", "properties"=>"2.8", "jmeter"=>"2.13 r1665067") {
xml.hashTree {
xml.TestPlan("guiclass"=>"TestPlanGui", "testclass"=>"TestPlan", "testname"=>"Stress Tests", "enabled"=>"true") {
xml.boolProp(false, "name"=>"TestPlan.functional_mode")
xml.boolProp(false, "name"=>"TestPlan.serialize_threadgroups")
xml.elementProp("name"=>"TestPlan.user_defined_variables", "elementType"=>"Arguments", "guiclass"=>"ArgumentsPanel", "testclass"=>"Arguments", "testname"=>"User Defined Variables", "enabled"=>"true"){
xml.collectionProp("name"=>"Arguments.arguments")
}
xml.stringProp("name"=>"TestPlan.user_define_classpath")
}
xml.hashTree {
xml.ThreadGroup("guiclass"=>"ThreadGroupGui", "testclass"=>"ThreadGroup", "testname"=>"Juvly API Performance Test", "enabled"=>"true"){
xml.stringProp("continue", "name"=>"TestPlan.serialize_threadgroups")
xml.elementProp("name"=>"ThreadGroup.main_controller", "elementType"=>"LoopController", "guiclass"=>"LoopControlPanel", "testclass"=>"LoopController", "testname"=>"Loop Controller", "enabled"=>"true") {
xml.boolProp(false, "name"=>"LoopController.continue_forever")
xml.stringProp(1, "name"=>"LoopController.loops")
}
xml.stringProp(1, "name"=>"ThreadGroup.num_threads")
xml.stringProp(1, "name"=>"ThreadGroup.ramp_time")
xml.boolProp(false, "name"=>"ThreadGroup.scheduler")
xml.stringProp("name"=>"ThreadGroup.duration")
xml.stringProp("name"=>"ThreadGroup.delay")
}
xml.hashTree {
requests.each do |request|
vars = request['url'].split('/').select{|p| p.match(/{{.+}}/)}.map{|v| v.gsub(/{{|}}/,'')}
vars.each do |v|
request[‘url’].gsub!(/{{|}}/, ”)
end
uri = URI(request['url'])
vars.each do |v|
uri.path.gsub!(/#{v}/, "${#{v}}")
end
xml.HTTPSamplerProxy("guiclass"=>"HttpTestSampleGui", "testclass"=>"HTTPSamplerProxy", "testname"=>"#{request['url']}", "enabled"=>"true"){
xml.elementProp("name"=>"HTTPsampler.Arguments", "elementType"=>"Arguments", "guiclass"=>"HTTPArgumentsPanel", "testclass"=>"Arguments", "enabled"=>"true"){
if(!request['body'].empty?)
xml.collectionProp("name"=>"Arguments.arguments"){
request['body']['formdata'].each do |formelement|
xml.elementProp("name"=>"#{formelement['key']}", "elementType"=>"HTTPArgument"){
xml.boolProp(false, "name"=>"HTTPArgument.always_encode")
xml.stringProp(formelement['key'], "name"=>"Argument.name")
xml.stringProp(formelement['value'], "name"=>"Argument.value")
xml.stringProp("=", "name"=>"Argument.metadata")
xml.boolProp(true, "name"=>"HTTPArgument.use_equals")
}
end
}
end
}
xml.stringProp("#{uri.host}", "name"=>"HTTPSampler.domain")
xml.stringProp("#{uri.port}", "name"=>"HTTPSampler.port")
xml.stringProp("name"=>"HTTPSampler.connect_timeout")
xml.stringProp("name"=>"HTTPSampler.response_timeout")
xml.stringProp("#{uri.scheme}", "name"=>"HTTPSampler.protocol")
xml.stringProp("name"=>"HTTPSampler.contentEncoding")
xml.stringProp("#{uri.path}", "name"=>"HTTPSampler.path")
xml.stringProp("#{request['method']}","name"=>"HTTPSampler.method")
xml.boolProp(true,"name"=>"HTTPSampler.follow_redirects")
xml.boolProp(false,"name"=>"HTTPSampler.auto_redirects")
xml.boolProp(true,"name"=>"HTTPSampler.use_keepalive")
xml.boolProp(true,"name"=>"HTTPSampler.DO_MULTIPART_POST")
xml.boolProp(true,"name"=>"HTTPSampler.BROWSER_COMPATIBLE_MULTIPART")
xml.boolProp(false,"name"=>"HTTPSampler.monitor")
xml.stringProp("name"=>"HTTPSampler.embedded_url_re")
}
xml.hashTree{
xml.HeaderManager("guiclass"=>"HeaderPanel", "testclass"=>"HeaderManager", "testname"=>"HTTP Header Manager", "enabled"=>"true"){
xml.collectionProp("name"=>"HeaderManager.headers"){
request['header'].each do |header|
xml.elementProp("name"=>"#{header['key']}", "elementType"=>"Header"){
xml.stringProp("#{header['key']}","name"=>"Header.name")
xml.stringProp("#{header['value']}","name"=>"Header.value")
}
end
}
}
if !request["vars"].nil?
xml.hashTree
request["vars"].each do |var|
xml.RegexExtractor("guiclass"=>"RegexExtractorGui", "testclass"=>"RegexExtractor", "testname"=>"Regular Expression Extractor", "enabled"=>"true"){
xml.stringProp(false,"name"=>"RegexExtractor.useHeaders")
xml.stringProp(var[:var_name],"name"=>"RegexExtractor.refname")
xml.stringProp("\"#{var[:page_value][:element]}\":\"(.+?)\"","name"=>"RegexExtractor.regex")
xml.stringProp("$1$","name"=>"RegexExtractor.template")
xml.stringProp(0,"name"=>"RegexExtractor.default")
xml.stringProp(1,"name"=>"RegexExtractor.match_number")
}
xml.hashTree
end
end
}
end
}
}
}
}
end
[/code]
  • Finally we generate output jmx file that we can use for JMeter
    [code lang="ruby"]
outFile = File.new(out_file, "w+")
outFile.puts builder.to_xml
outFile.close
[/code]

So now we have a file that you need to open in JMeter UI, configure number of threads that you want to execute and you are good to go.

As promised here is a link to Scimus repository, where we upload examples and tools that we use for testing. If you can add something on fix, some parts of a code you are welcomed there.

Thank you for attention and hope it was useful for someone out there!

LinkedIn

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