Bugzilla

Just my two cents worth.
I am testing TB under linux for like 10 years.
I have used the following set up to run tests in separate window manager inside Xephyr so that I can monitor the progress while I do other things on the desktop (and actually my linux runs inside VirtualBox (previously inside VMPlayer) under Windows. Just fine. (you DO need memory to run this combination).

This is from within a bash script.
```
    # July 12, 2019. tryserver uses the following size 1600x1200.
    SIZE=1600x1200

#   -br     sets  the default root window to solid black instead of the standard root weave pattern.
#          This is the default unless -retro or -wr is specified.

#       -ac     disables host-based access control mechanisms.  Enables access by any host, and  permits
#               any  host  to  modify  the  access control list.  Use with extreme caution.  This option
#               exists primarily for running test suites remotely.

#       -noreset
#               prevents a server reset when the last client connection is  closed.   This  overrides  a
#               previous -terminate command line option.


    Xephyr -ac -br -noreset -screen $SIZE :2 &
    # was DISPLAY=localhost:2.0 before Oct 27, 2016
    DISPLAY=:2.0
    waitfor 5
    # oclock &
    xfwm4 &
```

Then I ran the script to invoke mochitest (prevously |make mozmill| test for  TB).

All runs well so far as far as I can tell.

Just my two cents worth.
I am testing TB under linux for like 10 years.
I have used the following setup to run tests in separate window manager inside Xephyr so that I can monitor the progress of local test while I do other things on the desktop. And actually my linux runs inside VirtualBox (previously inside VMPlayer) under Windows. 
The whole setup works just fine. (you DO need memory to run this combination).

This is from within a bash script.
```
    # July 12, 2019. tryserver uses the following size 1600x1200.
    SIZE=1600x1200

#   -br     sets  the default root window to solid black instead of the standard root weave pattern.
#          This is the default unless -retro or -wr is specified.

#       -ac     disables host-based access control mechanisms.  Enables access by any host, and  permits
#               any  host  to  modify  the  access control list.  Use with extreme caution.  This option
#               exists primarily for running test suites remotely.

#       -noreset
#               prevents a server reset when the last client connection is  closed.   This  overrides  a
#               previous -terminate command line option.


    Xephyr -ac -br -noreset -screen $SIZE :2 &
    # was DISPLAY=localhost:2.0 before Oct 27, 2016
    DISPLAY=:2.0
    waitfor 5
    # oclock &
    xfwm4 &
```

Then I ran the script to invoke mochitest (prevously |make mozmill| test for  TB) within the same script. You may need to export DISPLAY variable depending on how your script is written.

All runs well so far as far as I can tell.

Just my two cents worth.
I am testing TB under linux for like 10 years.
I have used the following setup to run tests in separate window manager inside Xephyr so that I can monitor the progress of local test while I do other things on the desktop. And actually my linux runs inside VirtualBox (previously inside VMPlayer) under Windows. 
The whole setup works just fine. (you DO need memory to run this combination).

This is from within a bash script.
```
    # July 12, 2019. tryserver uses the following size 1600x1200.
    SIZE=1600x1200

#   -br     sets  the default root window to solid black instead of the standard root weave pattern.
#          This is the default unless -retro or -wr is specified.

#       -ac     disables host-based access control mechanisms.  Enables access by any host, and  permits
#               any  host  to  modify  the  access control list.  Use with extreme caution.  This option
#               exists primarily for running test suites remotely.

#       -noreset
#               prevents a server reset when the last client connection is  closed.   This  overrides  a
#               previous -terminate command line option.


    Xephyr -ac -br -noreset -screen $SIZE :2 &
    # was DISPLAY=localhost:2.0 before Oct 27, 2016
    DISPLAY=:2.0
    waitfor 5
    # oclock &
    xfwm4 &
```

Then I ran the script to invoke mochitest (prevously |make mozmill| test for  TB) within the same script. You may need to export DISPLAY variable depending on how your script is written.

I forgot to mention waitfor is a function in the script to wait for given seconds.
```
function waitfor
{
    i=$1
    # echo "i is $i"
    # should check for numeric, but the only caller is in this file.
    echo "Sleeping for $i seconds."
    while [ $i -gt 0 ]
    do
	echo -n "$i "
	sleep 1
	i=$(( i - 1 ))
    done
}
```

The verbose wait is to let developer know the sleep is caused by EXPLICT wait by the script, not the
strange sleep caused by the flaky test framework, etc.

All runs well so far as far as I can tell.

Just my two cents worth.
I am testing TB under linux for like 10 years.
I have used the following setup to run tests in separate window manager inside Xephyr so that I can monitor the progress of local test while I do other things on the desktop. And actually my linux runs inside VirtualBox (previously inside VMPlayer) under Windows. 
The whole setup works just fine. (you DO need memory to run this combination).

This is from within a bash script.
```
    # July 12, 2019. tryserver uses the following size 1600x1200.
    SIZE=1600x1200

#   -br     sets  the default root window to solid black instead of the standard root weave pattern.
#          This is the default unless -retro or -wr is specified.

#       -ac     disables host-based access control mechanisms.  Enables access by any host, and  permits
#               any  host  to  modify  the  access control list.  Use with extreme caution.  This option
#               exists primarily for running test suites remotely.

#       -noreset
#               prevents a server reset when the last client connection is  closed.   This  overrides  a
#               previous -terminate command line option.


    Xephyr -ac -br -noreset -screen $SIZE :2 &
    # was DISPLAY=localhost:2.0 before Oct 27, 2016
    DISPLAY=:2.0
    waitfor 5
    # oclock &
    xfwm4 &
```

Then I ran the script to invoke mochitest (prevously |make mozmill| test for  TB) within the same script. You may need to export DISPLAY variable depending on how your script is written.

I forgot to mention waitfor is a function in the script to wait for given seconds.
```
function waitfor
{
    i=$1
    # echo "i is $i"
    # should check for numeric, but the only caller is in this file.
    echo "Sleeping for $i seconds."
    while [ $i -gt 0 ]
    do
	echo -n "$i "
	sleep 1
	i=$(( i - 1 ))
    done
}
```

The verbose wait is to let developer know the sleep is caused by EXPLICT wait by the script, not the
strange sleep caused by the flaky test framework, etc.


xfmw4 is the lightweight window manager that I use. This works fine. (I use it for my desktop, too.). YMMV.  
All runs well so far as far as I can tell.