커버리지와 가스 보고서

Two metrics help judge contract quality:

• Code coverage — how much of your Solidity is exercised by tests.
• Gas usage — how expensive your functions are to call.

Both are available as Hardhat plugins, and the Toolbox includes the gas reporter.

Coverage measures the percentage of statements, branches, and functions touched by your tests.

• Low coverage means untested code paths — potential hidden bugs.
• 100% coverage does not guarantee correctness, but gaps are red flags.

The solidity-coverage plugin instruments your contracts and reports coverage:

Then require it in your config:

Run the coverage task to execute your tests with instrumentation:

It prints a table per file and writes an HTML report to coverage/ you can open in a browser.

The report has four columns:

• % Stmts — statements executed.
• % Branch — if/else branches taken.
• % Funcs — functions called.
• % Lines — lines reached.

Branch coverage is often the hardest to fill — make sure both sides of every condition are tested.

The hardhat-gas-reporter (in the Toolbox) prints gas costs for each function call during tests. Enable it in config:

It outputs a table after npx hardhat test.

The gas report shows, per method:

• Min / Max / Avg gas across calls.
• # calls — how often it ran in tests.
• Deployment cost for each contract.

Functions that vary widely between min and max often have conditional logic worth examining.

The gas reporter can show estimated costs in real money by fetching a gas price and token price:

This helps you communicate the real cost of operations to stakeholders.

Coverage and gas reporting slow tests down, so gate them behind an environment variable:

Run REPORT_GAS=true npx hardhat test only when you need the report.

In continuous integration you can:

• Fail the build if coverage drops below a threshold.
• Comment gas diffs on pull requests.

These guardrails keep quality from silently regressing as the codebase grows.

The gas reporter can write its table to a file for archiving or diffing in CI:

Disabling colors keeps the file readable. Coverage similarly produces a coverage/ HTML report and an lcov.info file.

You learned to measure test and gas quality.

• solidity-coverage reports statement, branch, function, and line coverage via npx hardhat coverage.
• Branch coverage best reveals untested paths.
• The gas reporter (in the Toolbox) prints per-method gas and deployment costs.
• It can price calls in fiat and be toggled with an env var.
• Enforce thresholds in CI to prevent regressions.