Write validators in the validators folder, and supporting functions in the lib folder using .ak as a file extension.

For example, as validators/always_true.ak

validator {
  fn spend(_datum: Data, _redeemer: Data, _context: Data) -> Bool {
    True
  }
}

aiken build

You can write tests in any module using the test keyword. For example:

test foo() {
  1 + 1 == 2
}

To run all tests, simply do:

aiken check

To run only tests matching the string foo, do:

aiken check -m foo

If you're writing a library, you might want to generate an HTML documentation for it.

Use:

aiken docs

Find more on the Aiken's user manual.