coverage-analysis

Test Coverage Analysis

Running Coverage

# Basic coverage report
forge coverage

# Output:
# | File               | % Lines         | % Statements    | % Branches      | % Functions     |
# |--------------------|-----------------|-----------------|-----------------|-----------------|
# | src/Vault.sol      | 92.31% (36/39)  | 89.47% (34/38)  | 75.00% (12/16)  | 100.00% (8/8)  |
# | src/Token.sol      | 100.00% (12/12) | 100.00% (10/10) | 100.00% (4/4)   | 100.00% (3/3)  |

LCOV Output for Visualization

# Generate lcov.info
forge coverage --report lcov

# View in VS Code with "Coverage Gutters" extension
# Or generate HTML report:
genhtml lcov.info -o coverage-report --branch-coverage
open coverage-report/index.html

Coverage Types

Type	Meaning	Priority
Line	Was this line executed?	Medium
Statement	Was this statement executed?	Medium
Branch	Were both sides of if/else taken?	High
Function	Was this function called?	Low

Branch coverage is the most important for security — untested branches are where bugs hide.

Filtering Coverage

# Exclude test files and scripts
forge coverage --report lcov

# Filter the lcov output
lcov --remove lcov.info 'test/*' 'script/*' 'node_modules/*' \
     --output-file lcov-filtered.info

Coverage-Driven Testing Workflow

1. Identify Gaps

# Generate and inspect coverage
forge coverage --report lcov
genhtml lcov.info -o coverage-report --branch-coverage

2. Focus on Uncovered Branches

For each uncovered branch, write a targeted test:

// If coverage shows this branch is untested:
//   if (amount > maxDeposit) revert ExceedsMax();

function test_depositExceedsMax() public {
    uint256 maxDeposit = vault.maxDeposit(address(this));
    vm.expectRevert(abi.encodeWithSelector(ExceedsMax.selector));
    vault.deposit(maxDeposit + 1, address(this));
}

3. Common Untested Paths