_Follow along with this video:_ --- ### Analyzing the Counter contracts Continuing from the previous lesson, the `forge init` populated our project with the `Counter` files. #### Counter.sol It's a simple smart contract that stores a number. You have a function to `setNumber` where you specify a `newNumber` which is a `uint256`, and store it, and you have a function to `increment` the number. **Note:** `number++` is equivalent to `number = number + 1`. #### Counter.s.sol Just a placeholder, it doesn't do anything #### Counter.t.sol This is the interesting part. We haven't talked that much about carrying tests using Foundry. This is an essential step for any project. The `test` folder will become our new home throughout this course. Please run the following command in your terminal: ``` forge test ``` After the contracts are compiled you will see an output related to tests: - How many tests were found; - In which file; - Did they pass or not?; - Summary; ### How does `forge test` work? `forge test` has a lot of options that allow you to configure what is tested, how the results are displayed, where is the test conducted and many more! Run `forge test --help` to explore the options. I suggest reading [this page](https://book.getfoundry.sh/forge/tests) and navigating deeper into the Foundry Book to discover how tests work. But in short, in our specific case: 1. Forge identified all the files in the test folder, went into the only file available and ran the `setUp` function. 2. After the setup is performed it goes from top to bottom in search of public/external functions that start with `test`. 3. All of them will be called and the conclusion of their execution will be displayed. By that we mean it will run all the `assert` statements it can find and if all evaluate to `true` then the test will pass. If one of the `assert` statements evaluates to `false` the test will fail.