Regression Test Generator
Build regression tests that catch bugs before they ship
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When you fix a bug, what stops it coming back in four months? Is there a test named after it, or just a commit message? Regression Test Generator writes the test that pins a fixed bug in place, so the next refactor cannot quietly undo your work.
Short answer: Regression Test Generator writes the tests that lock in behaviour you have already fixed, reproducing the original bug conditions in your own test framework, so that any future change reintroducing the fault fails the suite immediately.
What is Regression Test Generator?
Regression Test Generator is a free tool for the last step of a bug fix. You paste the code or describe the function along with what went wrong, and it produces tests that capture the corrected behaviour. The point is not coverage for its own sake. It is a permanent record, in executable form, of a mistake your team has already paid for once.
Where It Fits In A Bug Fix
- Reproduce the bug and understand why it happens.
- Write or generate the failing test before the fix goes in.
- Apply the fix and watch the test turn green.
- Keep the test, named after the behaviour rather than the ticket number.
Generating the test at step two matters. A test written after the fix proves the code passes today, while a test written before it proves the test would have caught the bug at all.
What To Paste With The Bug
- ✅ The function or the relevant code path
- ✅ The input that triggered the fault
- ✅ What happened, and what should have happened
- ✅ Any state that mattered, such as an empty table or an expired token
Tip Describe the conditions rather than the fix. A test built around your implementation breaks on the next refactor. A test built around the behaviour survives it, which is the entire purpose of a regression suite.
How Does Regression Test Generator Work?
Paste the code or description into the prompt box, then set the options that decide the shape of the output.
| Option | What it changes | Suggested value |
|---|---|---|
| Language | The syntax of the generated tests | Auto-Detect when you paste real code |
| Test Framework | Jest, PyTest, JUnit, PHPUnit and others | The framework the project already runs |
| Test Type | Unit, integration, negative, end to end and more | Unit for a single function, Integration when state is involved |
| Coverage Level | Basic, Standard, Thorough or Exhaustive | Standard, since a regression test should be narrow |
Include Mocks helps when the bug involved an external call, Add Assertions writes the expected results, and Add Comments records why the test exists, which is the note your future self will need.
Behaviour pinned down
The corrected behaviour becomes executable, so the fix cannot silently disappear.
Context preserved
A comment explaining the original fault stops someone deleting the test as redundant.
Fast to add
The test exists before the pull request rather than in a follow up ticket nobody picks up.
What A Passing Suite Does Not Prove
It proves the specific faults you recorded have not returned. It says nothing about new ones, and a suite full of regression tests can grow slow and brittle if every case is added without thought. Keep them narrow, name them for the behaviour, and delete the ones that test a feature you removed. When a fix itself is the problem, paste the failure into the Error Fixer and work back from there.
Nothing here is metered, and EizTools opens with no login and no charge per run. The model selector lets you generate the same test in a different style when the first version depends too heavily on implementation detail. Regression Test Generator sits with the testing tools in the coding tools category, each carrying its own options.
Frequently Asked Questions
Should I write the test before or after the fix?
Before, whenever you can. A test that fails first and passes after the fix has proved it can detect the bug, which a test written afterwards never demonstrates.
How specific should a regression test be?
Specific about the behaviour, loose about the implementation. Assert on the outcome the user sees rather than on which internal method was called.
What if the bug needs a lot of setup?
Describe the state in the prompt and switch on Include Mocks. Complex setup is a sign the test may belong at integration level rather than as a unit test.
Do these tests replace normal unit tests?
No. They cover faults you have already met. Ordinary tests cover intended behaviour, and a healthy suite needs both kinds working together.
Every team has a bug that came back, usually after a refactor nobody connected to it. A test written at the moment of the fix is the cheapest insurance available, and generating it removes the last excuse for leaving it until later.
Sabir Bepari
Founder of EizTools and a passionate AI enthusiast dedicated to building practical, user-friendly AI tools that simplify everyday tasks.
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