How to write multiple unittests in dart in multiple files? - dart

Question

I am writing some Dart library and want to have it unittested. I created directory test and want to put my tests in here. Because I am going to have a lot of tests, I want to have them separated to multiple files. My questions is, what is the Dart convention, how to do that. I want to have my tests easily run all, however, I also want to be able to run just one file of tests.
What are your suggestions?

Answer 1

It is common to separate tests into multiple files. I am including an example of how you can do that.
Imagine that you have 2 files with tests, foo_test.dart, bar_test.dart that contain tests for your program. foo_test.dart could look something like this:
library foo_test;
import 'package:unittest/unittest.dart';
void main() {
test('foo test', () {
expect("foo".length, equals(3));
});
}
And bar_test.dart could look something like this:
library bar_test;
import 'package:unittest/unittest.dart';
void main() {
test('bar test', () {
expect("bar".length, equals(3));
});
}
You could run either file, and the test contained in that file would execute.
The, I would create something like an all_tests.dart file that would import the tests from foo_test.dart and bar_test.dart. Here is what all_tests.dart could look like:
import 'foo_test.dart' as foo_test;
import 'bar_test.dart' as bar_test;
void main() {
foo_test.main();
bar_test.main();
}
If you executed all_tests.dart, both the tests from foo_test.dart and bar_test.dart would execute.
One thing to note: for all this to work, you need to declare foo_test.dart and bar_test.dart as libraries (see the first line of each file). Then, in all_tests.dart, you can use import syntax to fetch the contents of the declared libraries.
This is how I organize most of my tests.

Answer 2

There is a tool that does exactly that, Dart Test Runner. An excerpt from that page:
Dart Test Runner will automatically detect and run all the tests in your Dart project in the correct environment (VM or Browser).
It detects any test writen in a file suffixed with _test.dart where your test code is inside a main() function. It doesn't have any problem detecting and running unittest tests.
It's pretty easy to install it and run it. Just two commands:
$ pub global activate test_runner
$ pub global run test_runner
For more options, please check Dart Test Runner page.

Answer 3

It's not necessary to have multiple files to isolate a test - see Running only a single test and Running a limited set of tests.
To isolate a test, change test() to solo_test().
So you can put all your tests in the same file (or into several parts).

Answer 4

In case it can be helpful for anybody while running a bunch of tests at once,
I was writing tests but my test file names did not end with *_test.dart
So I was not able to run all tests at once.
If you want to run all tests at once, it's mandatory to end your dart file with _test.dart.