Commercial Products

Getting Started

This document will get you started with Stella in about 5 minutes. By the end you'll be able to run sophisticated tests on your web applications.

Note: The current release of Stella (0.8) is in BETA status. That means Stella is still a work in progress, but I wanted to make it available as soon as it was useful.

This document covers the following steps:


You can download Stella as a tar or zip or install via Rubygems*:

  $ sudo gem install stella

**Note: Stella requires Ruby (1.8 or 1.9), or JRuby 1.3+. *

Test Plan Configuration

Test plans are written in Ruby, using a domain-specific syntax. That means that you can use the full power of Ruby in your configuration which is a critical part of running sophisticated tests.

The simplest possible usecase looks like this:

usecase do
  get "/"


Here is a more thorough example which combines several usecases into a single plan:

desc "Beverage Finder"
usecase 65, "Search" do

get "/", "Homepage" do wait 1..3 end

get "/search", "Search Results" do wait 2..3 param :what => "Sarsaparilla" param :where => "Lexington" response 200 do
listing = doc.css('div.listing').first set :lid, listing['id'].match(/(\d+)/)[0] end response 404 do quit "No results" end end

get "/listing/:lid", "Selected beverage"


usecase 25, "YAML API" do

get '/listings.yaml', "View All" do response 200 do
listings = doc.collect! { |l|; l[:id]; }

  <span class="n">set</span> <span class="ss">:listing_ids</span><span class="p">,</span> <span class="n">listings</span>
<span class="k">end</span>


get "/listing/:lid.yaml", "Select Listing" do param :lid => sequential(:listing_ids)
response 200 do repeat 7 end end


usecase 10, "Self-serve API" do

post "/listing/add", "Add a listing" do param :name => random(8) param :city => random(['Toronto', 'Vancouver', 'Montreal']) param :logo => file('logo.png') response 302 do repeat 3 end end



Running Stella

Stella is run from the command line like so:

$ stella [global options] COMMAND [command options]

The 3 main commands are: preview, verify, and generate.


The preview command parses and displays a test plan from the eyes of Stella. You use this command to ensure the test plan was written correctly an there are no errors.

$ stella preview -p path/2/example-2.rb
 Product Finder  (e66cfb)                                            
  Simple search  (6803c7)                                       65% 
    Homepage  (e374b3)                                            
      GET /
    Search Results  (a54d1e)                                      
      GET /search
    Selected listing  (1d303b)                                    
      GET /listing/:lid
  YAML API  (7adb64)                                            25% 
    View All  (7df521)                                            
      GET /listings.yaml
    Select Listing  (d8cadd)                                      
      GET /listing/:lid.yaml
  Self-serve API  (ba9e05)                                      10% 
    Add a listing  (1a3c2d)                                       


The verify command executes the test plan with a single virtual client (also known as a virtual user). You use this command to verify that your application and the test plan are functioning correctly.

$ stella verify -p path/2/example-2.rb hostname:port
 Product Finder  (e66cfb)                                           
 Simple search  (6803c7)                                                                         200                             200                       200
 YAML API  (7adb64)                                                                200                 200                 200                 200                 200                  200                  200                  200                  200
 Self-serve API  (ba9e05)                                                            302                        302                        302                        302

See stella verify -h for more info.


The generate command executes the test plan with 1 or more concurrent virtual clients. YOu use this command to see how your application performs under realistic load conditions.

$ stella generate -c 50 -p path/2/example-2.rb hostname:port
Preparing 50 virtual clients...
Generating requests for 1 reps...
Processing statistics...

 Product Finder  (e66cfb)                                                  
  Simple search  (6803c7)                                               65% 
   Homepage  (e374b3)                                                       
    GET /
      do_request                     0.189 <= 0.598s >= 1.492; 0.323(SD) 32(N)

   Search Results  (a54d1e)                                                 
    GET /search
      do_request                     0.030 <= 0.062s >= 0.248; 0.062(SD) 32(N)

   Selected listing  (1d303b)                                               
    GET /listing/:lid
      do_request                     0.032 <= 0.040s >= 0.061; 0.008(SD) 11(N)

   Sub Total:
      Total requests                 75 (200: 54, 404: 21)
       success                       75
       failed                        0
      do_request                     0.288s 0.344(SD)
      response_content_size          71.85KB      (avg:958.03B)

  YAML API  (7adb64)                                                    25% 
   View All  (7df521)                                                       
    GET /listings.yaml
      do_request                     0.683 <= 1.027s >= 1.326; 0.215(SD) 12(N)

   Select Listing  (d8cadd)                                                 
    GET /listing/:lid.yaml
      do_request                     0.041 <= 0.170s >= 0.356; 0.106(SD) 96(N)

   Sub Total:
      Total requests                 108 (200: 108)
       success                       108
       failed                        0
      do_request                     0.266s 0.296(SD)
      response_content_size          15.97KB      (avg:147.89B)

  Self-serve API  (ba9e05)                                              10% 
   Add a listing  (1a3c2d)                                                  
    POST /listing/add
      do_request                     0.107 <= 0.469s >= 1.030; 0.363(SD) 20(N)

   Sub Total:
      Total requests                 20 (302: 20)
       success                       20
       failed                        0
      do_request                     0.469s 0.363(SD)
      response_content_size          0.00B        (avg:0.00B)

      Total requests                 203
       success                       203 (req/s: 19.08)
       failed                        0
      do_request                     0.294s     0.325(SD)
      response_content_size          87.82KB      (avg:432.63B)

  max clients: 49
  repetitions: 1
    test time:      10.64s
    post time:       0.17s

This report needs some love but it contains some very useful data. The lines that look like 0.189 <= 0.598s >= 1.492; 0.323(SD) 32(N) refer to the minimum, mean, and maximum times along with the standard deviation and number samples.

See stella generate -h for more info.