lib_browser.dart

library coverage_141.browser;

import 'dart:html';

void browserA() {
  print('browserA');
}

void browserB() {
  print('browserB');
}

lib_vm.dart

library coverage_141.vm;

void vmA() {
  print('vm a');
}

void vmB() {
  print('vm b');
}

test_browser_test.dart

@TestOn('browser')
library coverage_141.test.browser_test;

import 'package:test/test.dart';

import 'package:coverage_141/browser.dart';

void main() {
  test('test browserA()', () {
    browserA();
  });
}

test_browser_test.html

<script type="application/dart" src="browser_test.dart"></script>

test_vm_test.dart

@TestOn('vm')
library coverage_141.test.vm_test;

import 'package:test/test.dart';

import 'package:coverage_141/vm.dart';

void main() {
  test('test vmA()', () {
    vmA();
  });
}