Branching Tree Technique (BTT) Skill

Write bulloak tree specifications for smart contract tests.

Bundled References

What is Bulloak?

Bulloak is a Solidity test generator that creates test scaffolds from .tree specification files. It offers a structured approach to test case design that ensures comprehensive coverage of all possible scenarios and edge cases in your smart contract tests.

Commands

To install Bulloak, if not found

cargo install bulloak

Generate test contract from a .tree file

bulloak scaffold -w --skip-modifiers --format-descriptions <path/to/file.tree>

where:

• -w writes the .t.sol only if it does not exist. Adding -f (-wf) overwrites an existing test and discards implemented bodies; to add tests for new branches, use bulloak check --fix --skip-modifiers --format-descriptions.
• --format-descriptions capitalizes the first letter of the branch in the test contract and add a period at the end of it.
• --skip-modifiers skips the generation of modifiers. We do this because we put all the modifiers in a separate Modifiers.sol file.

Check if the code in .t.sol file matches the specification in the .tree file

bulloak check --skip-modifiers <path/to/file.tree>

Important: Tree Files Should NOT Have Periods

Tree files should not have periods at the end of it branches. The --format-descriptions flag automatically:

1. Capitalizes the first letter
2. Adds a period at the end

# Correct (no period)
└── it should revert

# Wrong (has period)
└── it should revert.

Tree Syntax

Structure

FunctionName_ContractName_Integration_Test
├── condition1
│  └── outcome1
└── condition2
   └── outcome2

Terminology

• when and given become modifiers if they have nested branches.

Spec

1. In case of single tree per file, the root should be just the function name followed by _Integration_Concrete_Test.
2. In case of multiple trees in the same file, each root must be Contract::function, using :: as a separator, and all roots must share the same contract name (e.g., Foo::hashPair, Foo::min).
3. bulloak expects you to use ├ and └ characters to denote branches
4. If a branch starts with either when or given, it is a condition. when and given are interchangeable.
5. If a branch starts with it, it is an action. Any child branch an action has is called an action description.

Examples

For examples, see ./references/examples.md.

Rules

1. The test file must be placed in the tests/integration/concrete/{function} directory.
2. The directory name must use - format. For example, if the function name is createFlowStream, the corrresponding test tree and test file must be placed in the tests/integration/concrete/create-flow-stream directory.
3. The tree file name must be {function}.tree.
4. The test file name must be {function}.t.sol.
5. The root node of the spec and the Contract name must be {FunctionName}_Integration_Concrete_Test.

Workflow

1. Create the Tree File

Location for tree file: tests/integration/concrete/{function-name}/{functionName}.tree

Note: Your repo's agent will provide the exact directory structure.

2. Generate Test Scaffold

bulloak scaffold -w --skip-modifiers --format-descriptions <path/to/file.tree>

This generates a .t.sol file.

3. Check Tree-Test Alignment

bulloak check --skip-modifiers <path/to/file.tree>

If it returns false, your repo agent will look into it and fix the issues.

Best Practices

1. Order Conditions Logically

Start with guard conditions that cause early reverts:

├── when delegate call          // First: delegation check
│  └── it should revert
└── when no delegate call
   ├── given null               // Second: existence check
   │  └── it should revert
   └── given not null
      ├── when amount zero      // Third: input validation
      │  └── it should revert
      └── when amount not zero
         └── ...                // Finally: business logic

2. Use Consistent Terminology

Some examples below:

Whenever possible, try to use less words and more concise language for the branches.

3. Group Related Conditions

└── when withdrawal address not zero
   ├── when withdrawal address not owner    // Non-owner cases
   │  ├── when caller sender
   │  ├── when caller unknown
   │  └── when caller recipient
   └── when withdrawal address owner        // Owner cases
      └── ...

4. Detailed Leaf Nodes for Happy Path

For success cases, enumerate all side effects:

└── it should make the withdrawal
   ├── it should reduce the entry balance by the withdrawn amount
   ├── it should reduce the aggregate amount by the withdrawn amount
   ├── it should update the entry state
   ├── it should update the timestamp
   └── it should emit {Transfer}, {Withdraw} and {MetadataUpdate} events

Put events in parenthesis: {EventName}.

5. Don't Add a Modifier with the Same Name as the Function

A test function should NEVER have a modifier that matches its own name. The function name already encodes the condition — adding a same-name modifier is redundant.

// WRONG: modifier matches the function name
function test_WhenWithdrawAmountNotZero()
    external
    whenWithdrawalAddressNotZero
    whenWithdrawAmountNotZero // <- WRONG: redundant, same as the function name
{ }

// CORRECT:
function test_WhenWithdrawAmountNotZero() external whenWithdrawalAddressNotZero { }

6. Use proper indentation

Child branch symbols (├/└) must align with the tail of parent's └── or ├── (3 spaces, not 4):

└── when withdrawal address not zero
   ├── when withdrawal address not owner    ✓ Correct (3 spaces)
   │  └── when caller sender

Running Bulloak

# Scaffold tests from tree
bulloak scaffold -w --skip-modifiers --format-descriptions <path/to/file.tree>

# Check all trees in a directory
bulloak check --skip-modifiers tests/**/*.tree

Full Documentation

https://github.com/alexfertel/bulloak/blob/main/README.md

Example Invocations

Test this skill with these prompts:

1. Basic tree: "Write a BTT tree for a deposit function that reverts when amount is zero and succeeds otherwise"
2. Complex tree: "Create a tree spec for withdraw that checks null stream, caller authorization, and amount validation"
3. Sablier-specific: "Write a BTT tree for cancel in the Lockup protocol with proper stream state checks"