Microsoft Edge browser testing notes

Windows 10 is deprecating the old Microsoft Internet Explorer browser in favor of the new Microsoft Edge, with an updated rendering engine that is significantly more compatible with other modern browsers.

Since many MediaWiki developers run on Mac OS X or GNU/Linux systems, a few notes about compatibility testing with Edge may be helpful.

Documentation
The Edge team maintains a changelog for each release and preview build; this covers web platform features but doesn't always mention rendering bug fixes.

Upcoming web platform/DOM features are listed on the Platform Status page.

Getting Edge
Edge is bundled with Windows 10, which is widely available but not freely redistributable.

Testing VMs for Windows 10 + Edge are available alongside the older IE testing VMs, however beware they may be very out of date and will require installing updates before testing. See below for more about the release cadence, and  for how to get prerelease versions.

Filing bugs
Microsoft's public bug reporting system is Microsoft Connect; you will need log in with a Microsoft account (same as Xbox Live, Hotmail, or anything else using Microsoft Passport auth). Include a link to any Connect bug reports on the Phabricator side and vice versa to make sure we don't get lost. You may also want to add them to User:Catrope/IE bugs.

If you get feedback on your Connect bug, be sure to update the Phab bug with status.

Debugging tools
The 'F12 developer tools' on desktop/tablet are pretty good, comparable to the the debuggers in Firefox, Chrome, and Safari/WebKit.

On mobile, a remote debugger can be connected from Visual Studio 2015. This is free-as-in-beer but a fairly substantial installation.

Automation
Good question. Anyone know anything? :)

IE/Trident heritage
The Edge engine is based on MSIE's older Trident engine, but removes a lot of old IE-only features, adds a lot of modern stuff, and generally makes a bajillion improvements.

Old IE-specific workarounds should not simply add checks for Edge -- as much as possible, treat Edge like any other modern browser, and introduce checks around specific feature availability or bug detection if possible.

Note that IE 11, while still included in Windows 10 as an optional tool, is no longer receiving bug fixes other than critical security issues. Any bugs found in IE should be double-checked against Edge, but bugs should only be filed with Microsoft for those that remain in Edge.

Windows and Edge versioning
There are significant differences from Internet Explorer:
 * Edge is only available on Windows 10. There is no version of Edge for Windows 7/8/8.1.
 * Windows 10 and Edge are updated together; Edge's rendering engine is a system component.
 * It can be assumed that most Windows 10 users will receive timely updates, but there may be stragglers.
 * Windows 10 is updated much more aggressively than older releases of Windows, with multiple major updates planned per year.
 * August 2015 RTM: Edge 12 / Windows build 10240
 * November 2015 "1511 update": Edge 13 / Windows build 10586
 * June 2016 next expected update
 * Beware of old testing VMs! If you have a test VM that's still on 10240 you may need to let it update to get behavior consistent with what your users see.

Windows Insider preview builds
Any Windows 10 system can opt in to the "Window Insider" program to receive preview builds before major Windows 10/Edge updates go to wide release. However there are some gotchas:
 * There may be a delay of several hours from the opt-in before preview updates appear in Windows Update. This is extremely annoying when setting up a new test machine.
 * It is possible to revert to the current release, but consider using a spare machine or cloning an existing VM in case of explosions.
 * There are multiple "rings" of update schedules; select the "fast" ring to get the latest updates.
 * Occasionally preview features are broken or incomplete! Beware that some end-users will be using these Windows 10 Insider preview builds; so breakages unique to those versions are possible.

Device families
The same Edge engine is used on multiple Microsoft platforms, kept more or less in sync:
 * The exact same browser is used in both 'desktop' and 'tablet' modes (Windows 8/8.1 had separate 'Desktop' and 'Modern' IE variants)
 * Windows 10 Mobile for phones uses the exact same Edge rendering engine and shell app (UI layout depends on screen size)
 * Xbox One also includes the Edge browser