Sometimes, there is a need to generate data to test your code. While “testing in production” is a sweet spot to be, there are times when you need to “force” (stub) data that reflects certain business phenomena in production.

This does not mean “chaos engineering” but rather a finite set that can be ingested into a suite of integration tests to increase confidence in code change.

For example, creating a number of threads to generate load can be done trivially with Apache Bench (ab), I’m looking for a scenario builder with lots of traffic data. I’m referring to the “needle in the haystack” scenario builder.

I started with some ideas on how to create multiple “stubs” in a thread pool so that I can force concurrent payloads to hit a service to test. Using the Spring Framework and Spring Boot, this task became super simple. I ended up with the following:

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   @Async("myThreadPoolTaskExecutor")
   public Object createPayload() {
     // return payload pojo
   }

and the following TaskExecutor bean:

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   @Bean(name = "myThreadPoolTaskExecutor")
   public TaskExecutor threadPoolTaskExecutor() {
      ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
      executor.setCorePoolSize(4);
      executor.setMaxPoolSize(4);
      executor.setThreadNamePrefix("executor");
      executor.initialize();
      return executor;
    }

Of course, this is only a start with the following potential test:

• “Transaction boundaries” defined in my code.
• Verify the “concurrency” setup.
• Create a set of scenarios (the needle in the haystack)

I’ll update more on this journey as I add more to the data generator project I have been creating.