Introducing the Simula Template Engine

March 9, 2018


We have awesome news!

API Simulator release 0.8.2 is out and it makes available the all-new Simula Template Engine for API simulations response templating. Modeling API Simulations and configuring dynamic responses using intuitive YAML DSL (Domain Specific Language) is now easier and more flexible than ever before.

Simula Template Engine

Simula takes a template and combines it with data values to produce HTTP response. Status code and reason, standard and custom header fields, text or binary body content – Simula can produce them all, dynamically.

A Simula template consists of fragments. Some fragments do not change – they become part of the output. Other fragments – placeholders and scriptlets – can produce variable content:

  • Placeholders get resolved to actual values as part of rendering the template and, optionally, with formatting applied. Current and relative date/time, parameters from the request that change between calls, randomly generated numbers, date/time values, tokens from a pattern, data looked up in a CSV file or external SQL data store…they can all be source for placeholder values in a Simula template.
  • Scriptlets are code. The template engine executes the code upon rendering the template. Scriptlets may produce output or control its production via loops (“for”, while”, etc.), “if…else” statements, and more. Using scriptlets is not required. In some cases though, they can make it easy to process complex data like iterating over a list of values. Scripting is still supported, too.

As before, API Simulator streams out the HTTP response produced by a Simula template so that it can handle large content, even bigger than 2GB, with only few MB of memory.


This brief summary of Simula’s capabilities can tell only so much. We invite you to learn more about Simula, download and install API Simulator and run the examples. Why not even create API simulations to help your testing and development? We can help with that, too, if needed!

Let us know what you think at [feedback at]. Many thanks for your interest and support!


Happy API Simulations!