Question

I’m trying to convert the following Node.js test to Dart:

var fs = require('fs');
exports.asyncTest = function(test){
  fs.stat('test.txt', function(err, stats) {
    test.expect(2);
    test.strictEqual(err, null);
    test.notStrictEqual(stats.size, 0);
    test.done();
  })
};

So far I have:

import 'package:unittest/unittest.dart';
import 'dart:io';

main() {
  test('File is not empty', () {
    var stats = new File('test.txt').length().then(
      expectAsync1((v) {
        expect(v, isNot(0));
      }));
  });
}

This works but I’d like the test to fail instead of terminating if the file is not found. How is this accomplished?

Answer 1

You can use the exists() method on File.
File.exists() returns a Future<bool>, so do something like this.

main(){
  test('File Exists, and is not empty', () {
    var f = new File('test.txt');
    f.exists().then(expectAsync1((v) {
      expect(v, true);
      if (v)
        f.length().then(expectAsync1((l) => expect(l, isNot(0))));
    }));
  });
}

And of course this would be a lot prettier if it was made into two tests. A “file exists”, and a “file not empty”, in which the latter is only run if the first one passes.
But I have not been looking enough into the unittest library to see how you can make tests dependant of each other.