Thursday, 27 April 2017

Cucumber @After en @Before Hooks

We're using Cucumber at work to write tests, end-to-end-tests that access the user interface of the web application using Selenium.

I recently added an @After hook to a class that contained my StepDefinitions.

However, this @After hook was also called by all other scenarios1, which was not my intention.

As a matter of fact, that @After I added was executing similar code as an @After in another StepDefinition class. I verified that both @After annotated methods were executed for each and every scenario, and they were.

So I decided to move all @After annotated methods into a "GlobalStepDefinition" class, and collaps all of them into one method.

Incidentally, reference [3] shows why we should not have many of these end-to-end tests.


[1] GitHub Issues - Before and After methods invoked for unused step definition classes #1005
[2] Cucumber - Polymorphic Step Definitions
[3] - TestPyramid

Sunday, 23 April 2017

Problems with Resolution and My Monitor in Fedora Core 25

Well, my monitor always has been a bit of a problem child, but it worked, so I didn't mind.

I let it bounce once on the floor, but besides some slight discolouring in the lower-right corner, it was fine.

It reports EDID settings that are completely crap, but I got used to ignoring those, using xrandr.

XRandr settings that work for me

The following settings work:
xrandr --newmode "1920x1440" 339.50  1920 2072 2280 2640  1440 1443 1447 1514 -
xrandr --addmode VGA-0 1920x1440
xrandr --newmode "1600x1200" 235.00  1600 1728 1896 2192  1200 1203 1207 1262 -
xrandr --addmode VGA-0 1600x1200
xrandr --newmode "1280x1024"  159.50  1280 1376 1512 1744  1024 1027 1034 1078
xrandr --addmode VGA-0 1280x1024
xrandr --output VGA-0 --mode 1920x1440


Then I upgraded to Fedora Core 25, and my monitor showed me a handsome 1024x768, which was a disappointment to say the least. (I'm used to 1920x1440.)

Using xrandr gave me the cryptic error message:
bash-4.3$ xrandr --output XWAYLAND0 --mode "1920x1440"
xrandr: Configure crtc 0 failed
After some research I noticed that Fedora Core 25 is the first one to use Wayland1 as the default.


Switching back to the old Xorg2 fixed my problem.

Checking graphics card

bash-4.3$  lspci -nnk |grep -A 3 -i vga
01:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Juniper XT [Radeon HD 5770] [1002:68b8]
        Subsystem: ASUSTeK Computer Inc. Device [1043:0344]
        Kernel driver in use: radeon
        Kernel modules: radeon


[1] Wayland Desktop
[2] Fedora Project - Switching back to Xorg - how to install amd/ati driver on fedora 25?
AskFedora - How to add a custom resolution to Weyland Fedora 25?
ArchLinux - Forcing modes and EDID
Bugzilla Redhat - My Bugreport

Saturday, 15 April 2017

Keyset pagination

In the past I have used the MySQL equivalent of pagination. In other words, the splitting up of a ResultSet into pages of a fixed number of entries, by means of using SQL1.

It looks like the following:
SELECT * FROM tbl LIMIT 5,10;  # Retrieve rows 6-15
For compatibility with PostgreSQL, MySQL also supports the LIMIT row_count OFFSET offset syntax, which I've used in the past.


Performance is a key point here, as MySQL requires the retrieval of the results in order to determine where the offset starts.

If the table is large, retrieval of pages at the end of the table are going to be extremely slow.


A better way to deal with this, is to not use an offset, but use the key of the last row of the previous page, and use that in the query for the next page.

Obviously this only works if the resultset is sorted.

For more references that explain this a lot better, see [2] and [3].


[1] MySQL 5.7 - 14.2.9. SELECT Syntax
[2] Use the Index, Luke! - We need tool support for keyset pagination
[3] Use the Index, Luke! - Paging Through Results

Thursday, 6 April 2017

Try Git

To anyone who is absolutely new to the exciting new world of Git1.

There seems to be a little website where you can try Git2, working in a (very very) limited sandbox environment.

What is Git?

If you wish to know what Git is, there are loads of interesting articles on teh interwebs that explain it very well.

But I did find the following explanation in the README provided with the source tar-ball:
The name "git" was given by Linus Torvalds when he wrote the very
first version. He described the tool as "the stupid content tracker"
and the name as (depending on your mood):

 - random three-letter combination that is pronounceable, and not
   actually used by any common UNIX command.  The fact that it is a
   mispronunciation of "get" may or may not be relevant.
 - stupid. contemptible and despicable. simple. Take your pick from the
   dictionary of slang.
 - "global information tracker": you're in a good mood, and it actually
   works for you. Angels sing, and a light suddenly fills the room.
 - "goddamn idiotic truckload of sh*t": when it breaks


[1] Git --distributed-is-the-new-centralized
[2] Try Git