f3270 is an open-source Java framework designed for automating functional and regression testing on IBM Mainframe (TN3270) applications. Unlike standard web testing tools like Selenium—which rely on the browser DOM—f3270 interacts directly with character-based terminal fields. It operates by wrapping the underlying s3270 terminal execution engine, allowing Java developers to read, write, and navigate “green screen” fields programmatically. Core Architecture & How it Works
The framework bridges Java code with the mainframe terminal through a series of structural dependencies:
The s3270 Subprocess: f3270 launches an underlying s3270 (or wc3270 for Windows) executable as a background process to communicate with the host.
Screen Scraping API: It processes the layout as a coordinate grid (typically 24 rows × 80 columns) to target explicit fields.
Headless and GUI Modes: Tests can be executed completely headless in CI/CD pipelines, or with a built-in terminal GUI panel for local debugging. Step-by-Step Implementation Guide 1. Prerequisites & Installation
You must install the local 3270 terminal binaries and include the library in your build configuration: