Bulloak is a free, open-source tool that generates Solidity test files from a branching tree description. It is built for smart contract developers who want a structured way to cover every condition in their code before deployment. The project is written in Rust with JavaScript and TypeScript components and released under the MIT license.
Instead of starting from an empty test file, you describe the conditions your contract checks and the outcome each path should produce. Bulloak turns that description into test scaffolding, which you then complete with real assertions. The project is actively maintained, with its latest version v0.9.2 and a code update dated March 14, 2026.
What Is the Branching Tree Technique?
The Branching Tree Technique is a method for designing tests from the logic of a function. You start at the root with the first condition, such as whether the caller is the owner, and create a branch for each possible answer. Each branch splits further until you reach a leaf that states the expected outcome.
The method is useful for smart contracts because Solidity functions often check several conditions in sequence, and a single missed case can leave a vulnerability untested. Writing the tree first forces you to name every condition explicitly. Bulloak takes that written tree and converts it into test code, so the design work and the test structure stay in sync.
Who Is Bulloak For?
Bulloak suits Solidity developers who already write tests and want a more systematic way to organize them. It is particularly relevant for teams maintaining contracts with many access checks, state transitions or error paths, where manual test lists tend to grow unevenly. Students learning smart contract security may also find it helpful, because drawing the tree makes the contract's logic easier to read.
It is less suited to someone who has never written a Solidity test. The generated output assumes you understand the contract under test and can write meaningful assertions. Treat Bulloak as a way to organize thinking, not as a substitute for knowing what the code should do.
How Tree-Based Test Generation Fits a Real Project
Consider a simple vault contract with a withdraw function. Its logic might check whether the contract is paused, whether the caller is authorized and whether the balance covers the requested amount. Each check creates a branch, and the leaves describe what should happen in each combination, such as a revert or a successful transfer.
Once the tree is written, Bulloak produces the skeleton of the matching test file. You then add fixtures, deploy the contract in the test environment and assert the expected revert messages or balances. When the contract changes, you update the tree and regenerate the structure, which keeps the test suite aligned with the logic.
Key features
Tree-based test design
Generated test scaffolding
Free and open source
How to install Bulloak on Windows
- 1
Get the release
Go to the official GitHub repository for Bulloak and open the Releases page. Look for the latest version, v0.9.2 at the time of writing, and check whether a Windows build is attached to the release. Download only from the official GitHub repository or its Releases page.
- 2
Verify the file
If the release lists a SHA-256 checksum or a signature, compare it with your downloaded file before running anything. In PowerShell, the Get-FileHash command prints the hash of a file. If the values do not match, delete the file and download it again.
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Place and run the program
Extract the archive to a folder you control, such as a dedicated tools directory. If you want to run it from any terminal, add that folder to your PATH. Open a new terminal window and confirm the program starts by checking its built-in help output.
How to use Bulloak
Bulloak works best when you plan the tree before generating any code. The workflow is short, but the thinking happens in the first steps.
- Pick one function in your contract that has several conditions, such as an access check followed by a balance check.
- List the conditions in the order the code evaluates them, and note the outcome for each path.
- Write the tree in the format Bulloak expects, using one branch per condition and one leaf per outcome.
- Run the program against your tree file to generate the Solidity test skeleton.
- Open the generated file and fill in the setup, such as deploying the contract and creating test accounts.
- Replace each placeholder with a concrete assertion, then run your test framework to confirm each path behaves as the tree describes.
Repeat the process when a function changes. Updating the tree first keeps the design and the tests in step.
Pros & cons
- Free to use under the MIT license
- Source code is public for review and modification
- Encourages complete coverage of every condition in a function
- Recently updated, with a code update dated March 14, 2026
- Focused scope that does one job well
- Generates test structure but does not write assertions for you
- Assumes familiarity with Solidity and the tree-based method
- Version 0.9.2 means the project is pre-1.0, so interfaces may still change
- Confirm Windows builds on the Releases page before relying on them
Is Bulloak safe?
Bulloak is a development tool that does not handle wallets, private keys or funds, so the main risks come from the download itself. Get the program only from the official GitHub repository or its Releases page. Compare the file against the SHA-256 checksum or signature the release publishes, and discard any file that does not match. Avoid copies on third-party download sites, since they may be modified. Review generated test files before committing them, as incorrect assertions can give false confidence. Check the official repository for the latest version before you install.
- Official source only. Download from github.com/alexfertel/bulloak. Ignore ads and lookalike domains.
- Check the SHA-256. Compare the installer hash with the value the developer publishes before running it.
- Never share your seed phrase. No developer, support agent or website — including CryptApps — will ever ask for it.
Alternatives
Bulloak has a narrow purpose: it turns a branching tree of conditions into Solidity test skeletons. Remix Desktop is a full IDE for writing, compiling and deploying contracts, so it covers a much broader workflow. Tenderly CLI focuses on debugging and monitoring contracts after they run, not on designing tests in advance. Foundry is a toolkit with its own testing framework, and Bulloak can be used alongside it to structure the test cases you write. The Solidity compiler itself is the foundation that all of these tools rely on, rather than a test generator.
Specifications
- Price
- Free
- Type
- Open source
- License
- MIT
- Latest version
- v0.9.2
- Last update
- 14 Mar 2026
- Windows support
- Likely (builds for Windows; check releases)
- Source code
- github.com/alexfertel/bulloak
Frequently asked questions
Bulloak is used to generate Solidity test skeletons from a tree that describes a contract's conditions and expected outcomes. Developers write the tree first, which makes it easier to see every path through a function. The generated files then need manual assertions before they can test anything meaningful.
Yes, Bulloak is free to use and is released under the MIT license. Its source code is publicly available on GitHub, so anyone can read, modify or redistribute it under the terms of that license. There is no paid version mentioned in its project details.
Windows builds are expected, but you should check the GitHub Releases page for a Windows file in the latest version. If one is attached, you can install it like any other command-line program. If not, the project's repository is the place to find build instructions.
It is safe to install when you download it from the official GitHub repository and verify the SHA-256 checksum or signature provided with the release. Bulloak does not handle wallets or private keys. Still, review any generated test code before relying on it, because the assertions are your responsibility.
Writing tests by hand often means listing cases from memory, which can leave gaps in complex functions. Bulloak starts from a tree of conditions, so each branch and outcome is accounted for in the structure. You still write the assertions, but the layout of the test suite follows the logic of the contract.
No, Bulloak does not replace a testing framework. It generates the structure of test files, which you then run with a framework such as Foundry. Think of it as a planning and scaffolding step that sits before the test runner executes your tests.
Yes, the project shows a code update dated March 14, 2026, and its latest version is v0.9.2. Recent activity suggests active development, but pre-1.0 versions can change between releases. Check the official repository for the newest version before you start a new project.
Verdict
Bulloak is a good fit for Solidity developers who want a disciplined way to plan and organize tests for functions with many conditions. It is free, open source and recently updated, which makes it easy to try without commitment. It is less suitable for beginners who have not yet written tests, because the tool assumes you can judge the logic and write meaningful assertions. Install it from the official repository, verify the download, and pair it with a full testing framework.