Use Coverage Gutters to better check contract Code Coverage.

For smart contract developers, writing contract tests is a very important skill. Maybe we don't need to be as rigorous as auditing, but testing must cover all functions. Code Coverage is usually needed to view the coverage.

Here, I recommend a plugin for VS Code called Coverage Gutters. It can locate the code covered/uncovered by your tests based on the Code Coverage Report file you generated, and prompt it in front of the line, making test writing more efficient.

Demo#

I use Foundry to create smart contract projects and perform contract testing.

mkdir demo && cd demo
forge init

After project initialization, the directory structure is as follows:

.
├── README.md
├── foundry.toml
├── lib
│   └── forge-std
├── script
│   └── Counter.s.sol
├── src
│   └── Counter.sol
└── test
    └── Counter.t.sol

6 directories, 5 files

Counter.sol contract file and the corresponding Counter.t.sol test file are automatically generated.

Install Coverage Gutters from the VS Code plugin marketplace.

coverage-gutters

Use Foundry to generate Code Coverage Report.

forge coverage --report lcov

Then you will find a lcov.info file generated.

After locating the window to the src/Counter.sol file, click on watch at the bottom.

watch

You can see that there is a green mark in front of the lines of code that have been covered by the test, and the coverage rate is displayed at the bottom as 100%.

shot-1

Modify test/Counter.t.sol and add a function.

function decrease() public {
    number--;
}

Update the Code Coverage Report.

forge coverage --report lcov

You will find that there is a red mark in front of the newly added untested function, and the coverage rate at the bottom becomes 67%.

shot-2