Random inputs in unit testing

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I recently had an upstream reviewer telling me that I should not randomise my test input because “randomness does not provide a useful input to the test and sets a bad example of practices for writing tests”.

I am going to explain here why this is wrong and it’s actually good practice to randomise inputs. Let me start by saying that random test failures are not the same thing as spurious test failures. I’ll come back to that later.

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Glen Rock State Forest

The latest Phantom 4 video shot at Glen Rock State Forest in South East Queensland’s Scenic Rim.

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Montville via Phantom 4

Enjoy the spectacular scenery of the Sunshine Coast Hinterland.

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Super Moon

While I was dropping my mother at the airport tonight, I thought I’d try to get a nice shot of the “super moon”. I wasn’t too disappointed with this result!

It’s hard to convey just how bright the moon is. I processed this shot so the detail stands out, but in real life it’s a glowing white ball.

Supermoon

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Another drone video on the Brisbane River

I tried to do some colour grading here. The range is spot on now, but I think I could increase the saturation a bit. Next time.

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LXD on Linode servers

I was recently trying to get LXD working on my Linode server, but was getting this error:

$ lxc launch ubuntu:16.04 wordpress       
Creating wordpress
Starting wordpress
error: Error calling 'lxd forkstart wordpress /var/lib/lxd/containers /var/log/lxd/wordpress/lxc.conf': err='exit status 1'
  lxc 20161010203338.247 ERROR lxc_seccomp - seccomp.c:get_new_ctx:224 - Seccomp error -17 (File exists) adding arch: 2
  lxc 20161010203338.247 ERROR lxc_start - start.c:lxc_init:430 - failed loading seccomp policy
  lxc 20161010203338.247 ERROR lxc_start - start.c:__lxc_start:1313 - failed to initialize the container

The fantastic Stéphane Graber helped me to work out that the default Linode kernel doesn’t have the right bits compiled into it, and I should be using an Ubuntu kernel instead.

So, following the guide at https://www.linode.com/docs/tools-reference/custom-kernels-distros/run-a-distribution-supplied-kernel-with-kvm to upgrade my kernel, it now works.

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Brisbane River Drone Flight

My second drone video! A bit longer, and has a special appearance by my dog at the end.

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Droning on!

I went and bought myself a DJI Phantom 4. Holy crap, I’m impressed. 12MP images and 4k video. Not to mention all the other bells and whistles like collision avoidance, auto return to home and when you put it in speed mode, it does 70km/h!

Here’s the first of a couple of videos I put together for it:

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Webex using Ubuntu LXD containers

If you read my previous post WebEx in Ubuntu LXC containers you’ll have learned how to get Cisco’s Webex running on Ubuntu in a 12.04 container.

I figured it was time to work out how to get it running in the newer LXD containers available in 16.04, here’s how I did it.

Install LXD

apt-get install lxd
sudo lxd init

When it asks you about networking, use the existing lxcbr0 bridge, do not let it use a new bridge as by default it will create lxdbr0. We need to stay on lxcbr0 so that networking continues to work in the old containers.

Create the LXD container

lxd init ubuntu:precise webex

This will download a new 12.04 template if you don’t already have one, it will take a while depending on your Internet connection.

Cheat by copying the old rootfs

I’m not going to rebuild my rootfs from scratch, the old one is perfectly usable! So as root, we can copy it from the old LXC area:

cp -rp /var/lib/lxc/webex/rootfs /var/lib/lxd/containers/webex/

Configure the container

The old container rootfs was a privileged container so we need to do the same on this LXD copy:

lxd config set webex security.privileged true

To make the sound device available you need to set up the sound device in the container. Here I am adding all the devices under /dev/snd/ on my own host, note that yours may differ so edit the commands accordingly:

lxc config device add webex /dev/snd/controlC0 unix-char path=/dev/snd/controlC0
lxc config device add webex /dev/snd/hwC0D0 unix-char path=/dev/snd/hwC0D0
lxc config device add webex /dev/snd/hwC0D3 unix-char path=/dev/snd/hwC0D3
lxc config device add webex /dev/snd/pcmC0D0p unix-char path=/dev/snd/pcmC0D0p
lxc config device add webex /dev/snd/pcmC0D3p unix-char path=/dev/snd/pcmC0D3p
lxc config device add webex /dev/snd/seq unix-char path=/dev/snd/seq
lxc config device add webex /dev/snd/timer unix-char path=/dev/snd/timer

You may remember I was using ssh X forwarding in the old container. We don’t need to do that any more as we can get direct access to the video from the container by using this config:

lxc config device add webex /dev/dri/card0 unix-char path=/dev/dri/card0
lxc config device add webex /dev/dri/controlD64 unix-char path=/dev/dri/controlD64
lxc config device add webex /dev/dri/renderD128 unix-char path=/dev/dri/renderD128
lxc config device add webex /dev/dri/fb0 unix-char path=/dev/fb0
lxc config device add webex /dev/video0 unix-char path=/dev/video0
lxc config device add webex X11 disk source=/tmp/.X11-unix path=/tmp/.X11-unix

Again your devices under /dev/dri may differ a little to mine, change accordingly.

Now, start the container and start a bash shell in it:

lxc start webex
lxc exec webex bash

You’ll now have a root prompt in the container. You can test that sound is working by doing something like:

sudo -u ubuntu aplay /usr/share/sounds/alsa/Front_Center.wav

In root’s home we need to make a script to start firefox for us, it looks like this:

root@webex:~# cat webex.sh  
#!/bin/bash 
DISPLAY=:0 su -c firefox - ubuntu

Make sure to chmod +x webex.sh

Now, all things being good, you can do this to launch Firefox:

lxc exec webex ./webex.sh

Launch Webex as you normally would and verify that it works. If it’s OK, you can remove the old SSH service as it’s not needed any more.

apt-get remove openssh-server

In my next post, I’ll explain how to convert the configuration into a more handy LXD profile that you can use for any container.

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On Successful Teams …

To build a successful team, you need several facets all working in harmony.

Self-motivation and desire

Successful teams consist of people who are self-motivated and have an innate desire to succeed.

Communication

It’s a cliché but good communication is essential. The team must be open, transparent and share details of its members’ work. Keeping secrets fosters mistrust.

Proactive

Good teams spend less time responding to external events and more time being proactive about making sure they are in control.

Adaptation and resilience

A good team is adaptive and resilient to change. A good team will be prepared to throw away work if it means a more successful outcome by doing something differently.

Decision making

Everyone should know how and by whom decisions are made.

Mutual support

Mutually supportive team members create something that is larger than the sum of their parts. They will be prepared to help each other at any time.

Reliability and predictability

If you are both reliable and predictable, you will succeed. This means not only delivering on time, but reliable to each other in the team.

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