Is there any good open-source software to write test cases?

I'd like to have historical memory of the test cases I usually do to verify a software suite, and the company in which I work now uses word or excel docs for this task, but I'd like something more focused on the type of task. What do you use? Is there any open-source software to fill with test cases?

Thanks

Is there any tool to write test cases?

Answer: There are several test management tools such as TestRail, PractiTest, QTest, Zephyr, etc. and are good for writing test cases.

Is Selenium an open-source testing tool?

Selenium is an open source testing tool that allows users to test web applications across different browsers and platforms. Selenium includes a suite of software that developers can use to automate web applications including IDE, RC, WebDriver and Selenium grid, which all serve different purposes.

TestLink is another very nice option; I highly recommend it.