What is the best way to unit test a commander cli?

[tiagoporto]

I would like to cover my cli (commander.js) with unit test.

What is the best way to do that?

[shadowspawn]

A couple of tips:

Have a function that creates a new Command object for your cli, so each test can use a fresh command.

If your tests include error cases detected by Commander, pass in some configuration when creating the command to make it easier to catch errors (.exitOverride()) or suppress output (configureOutput()).

[tiagoporto]

@shadowspawn do you have some examples to share, will be really helpful?
Thank you

[shadowspawn]

Example of a function to create the "program", with some extra options for using in unit tests:

• https://github.com/shadowspawn/forest-arborist/blob/fca5ffcc5b300660ae9e1f6c4a8667d72feb0822/src/command.ts#L48

I am not claiming this is the best way, just what I used! TypeScript example:

// ------------------------------------------------------------------------------
// Command line processing. Returning new object to allow multiple calls for testing.

export function makeProgram(options?: { exitOverride?: boolean, suppressOutput?: boolean }): Command {
  const program = new commander.Command();

  // Configuration
  if (options?.exitOverride) {
    program.exitOverride();
  }
  if (options?.suppressOutput) {
    program.configureOutput({
      writeOut: () => {},
      writeErr: () => {}
    });
  }

...

[tiagoporto]

Thank you.