Test4z: Unit Testing for Mainframe, With Confidence.

Usher in a new era of code change confidence and application vitality by empowering developers. With Test4z, developers apply the 6 Core Principles of unit testing using their tool of choice (VS Code, ISPF, Eclipse or other IDE).




Without a safety net, code changes can be perilous.

A lack of true unit tests is a reality for many teams and it prevents them from fully empowering their business leaders. Code changes are simply too slow, too costly, and too risky.

With Test4z, a component of the Broadcom Mainframe DevOps Suite, teams address this liability by equipping COBOL developers to do unit testing right.

"Does the change perform as expected?"

Answer YES with confidence!


6 Core Principles

Test4z is built on the 6 core unit testing principles, the gold standard:

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Keep Tests Small

Units should be the smallest testable part of the program. Test4z enables ‘microtests’ at the paragraph or section level.

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It’s essential to run tests in isolation from the rest of the system. Test4z offers advanced mocking capabilities across code, data, and subsystems.

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Maintain Tests

Tests should be easy to maintain. With Test4z, unit tests are maintained just like application code; they’re easily edited with updates to logic and variables. Templates help developers write clear, readable, and maintainable tests quickly.

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Continuous Integration

Whether using mainframe or distributed CI tools, automation must be simple. Test4z offers a convenient CLI that makes automation simple for developers. Swift and repeatable execution of tests via continuous integration provides developers with a rapid feedback loop.

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Keeping tests independent means the outcome of one test should not affect the outcome of another. In addition to native record/replay capabilities with automatic data capture, the Test4z CLI enables tests to be self-contained and run anywhere.

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Code Coverage

Alignment on code coverage between devs and managers is critical. Test4z offers native coverage visibility and nothing else needs to be installed.

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Test4z Developer Experience

Test4z offers COBOL developers an intuitive, friction-free experience. With Test4z, it’s easy to author and maintain tests.

  • Those who prefer VS Code/Code4z use the Unit Test for Mainframe extension (see demo video below)
  • Those who prefer Eclipse or other IDEs use the Test4z CLI
  • Those who prefer ISPF connect to Test4z directly

With Test4z, the tests are code, co-located with the application source. An API portfolio, which serves as an abstraction layer to simplify test case authoring, and a Runtime that executes tests and captures code coverage enable developers to easily apply the 6 Core Principles.

And tests can be run on any LPAR, including ZD&T, using Team Build, which is part of the solution.

Test4z is simple for devs to understand and use and there are no other tooling prerequisites.

See the VS Code Experience in Action

Project Sustainability

The benefits of unit testing done right propagate. Test4z unit tests can be reused for integration testing, regression testing, and other forms of functional testing in a CI/CD pipeline. Following this “golden path” ensures code quality, maintainability, and overall project success. 

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What our customers are saying

I LOVE this project!!!

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Our Principal Director was amazed by the tool and its simplicity.

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Finally, a tool for the mainframe that works like the distributed world.

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You've got the right product, vision & talent.

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This is AWESOME!!!

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No other solution like this exists.

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Continue Exploring


Mainframe Testing Blogs

Learn about automating unit tests and more, including best practices, tips & tricks, etc.



Developer Day-in-the-Life Article

Broadcom’s Peter Wassel explains unit testing the ‘DevOps way’ in this SHARE article.



Mainframe Testing Glossary/FAQs

Learn about the complete range of testing approaches and options including Test4z


Getting Started

By institutionalizing unit testing best practices with Test4z (i.e., the 6 Core Principles), teams fortify their code base thereby elevating confidence in code changes and inspiring product owners to find even more creative ways to leverage their mainframe assets.