Stefano Tommesani

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Unit-testing file I/O

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Two good news: file I/O is unit-testable, and it is surprisingly easy to do. Let's see how it works!

A software no-one asked for

First, we need a piece of software that deals with files and that has to be unit-tested. The TestableIO project does the following:

  • given a directory, enumerate all the lossless audio files (e.g. FLAC ones) and all the lossy audio files (e.g. MP3 ones),
  • if an audio file the same name is present in both lossless and lossy format, delete the lossy file
  • repeat for the subfolders of the given directory
Last Updated on Sunday, 26 November 2017 14:34
 

Fixing Git pull errors in SourceTree

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If you encounter the following error when pulling a repository in SourceTree:

VirtualAlloc pointer is null, Win32 error 487

it is due to to the Cygwin system failing to allocate a 5 MB large chunk of memory for its heap at the fixed address 0x68570000, while only a hole 2.5 MB large was apparently available there (see the whole thread on SO). Unfortunately, attempts to rebase MSYS or other tricks are not working, requiring a full reboot of the PC to properly complete pulls.

To resolve this problem once and for all, upgrade the Git used by SourceTree from version 1.x to version 2: click on Tools | Options, select the Git tab and check the version, in this case it is "System Git version 1.8.4".

GitUpdate1

Last Updated on Friday, 28 April 2017 13:12
 

Castle on the hill of crappy audio quality

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As the yearly dynamic range day is close (March 31st), let's have a look at one of the biggest audio massacres of the year, Ed Sheeran's "Castle on the hill". First time I heard the song, I thought my headphones just got broken, it's really that bad. So let's measure the Dynamic Range (DR) of the track:

CastleHillDR

Here is how the DR value is computed:

In order to determine the official DR value, a song or entire album (16 bit, 44.1 kHz wave format) is scanned. A histogram (loudness distribution diagram) is created with a resolution of 0.01 dB. The RMS – an established loudness measurement standard – is determined by gathering approximately 10,000 pieces of loudness information within a time span of 3 seconds (dB/RMS). From this result, only the loudest 20% is used for determining the average loudness of the loud passages. At the same time, the loudest peak is determined. The DR Value is the difference between the peak and the top 20 average RMS measurements (top 20 RMS minus Peak = DR). (from TT Dynamic Range Meter documentation)

 

Necessary evil: testing private methods

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Some might say that testing private methods should be avoided because it means not testing the contract, that is the interface implemented by the class, but the internal implementation of the class itself. Still, not all classes were designed with testability in mind, so real life compromises sometimes demand such a trick.

When writing unit tests in C# with MSTest, the PrivateObject class lets you easily call private methods:

  1. [TestMethod]
  2. public void TestLPRead()
  3. {
  4.   var Logger = A.Fake<ILogger>();
  5.   var Telemetry = A.Fake<ITelemetry>();
  6.   DefaultDataModel DM = new DefaultDataModel(Logger, Telemetry);
  7.   PrivateObject obj = new PrivateObject(DM);
  8.   List<LPRead> ReadsList = (List<LPRead>)obj.Invoke("GetReads");

In the code above, a PrivateObject instance is created passing an instance of the class to be tested

  1. PrivateObject obj = new PrivateObject(DM);

then the invocation of the private method, that would be

  1. List<LPRead> ReadsList = DM.GetReads();

if the method were public, becomes

  1. List<LPRead> ReadsList = (List<LPRead>)obj.Invoke("GetReads");
Last Updated on Sunday, 29 January 2017 22:39
 

I am right and you are wrong

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Objectivity3Have you ever convinced anyone that disagreed with you about a deeply held belief?

Better yet, have you changed your mind lately on an important topic after discussing with someone else that did not share your point of view?

Let's face it, if the topic of the discussion is not trivial, it is far easier to just keep repeating our (obviously bullet-proof) reasons and wonder why others don't just recognize our view as being the "correct" one. And we have proof that, the wider the gap between our own views and those of someone who disagrees with us, the stronger the impact of Naïve realism, and so we find no phenomenological trace of self-interested bias in the way we have considered the pertinent arguments.

Last Updated on Wednesday, 28 December 2016 15:47
 

How Commercial Insight changes R&D

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The CEB's Commercial Insight is based on three pillars:

  1. Be credible/relevant – Demonstrate an understanding of the customer’s world, substantiating claims with real-world evidence.
  2. Be frame-breaking – Disrupt the customer’s current logic, revealing an underappreciated aspect of the customer’s environment or a flawed assumption.
  3. Lead back to your unique strengths – Refer customers specifically to areas where you outperform competitors

Points #2 and #3 are critical to avoid the commoditization of solutions, the worst scenario for suppliers, as the buyers are satisfied with a limited set of functionalities shared among several products of competing companies and trigger a price-based war. The CEB research shows that most times suppliers are asked for a proposal when the internal process is around 57%, usually very close to an official RFP, where the the project already has shaped up and it is increasingly difficult to steer it to the strong, distinguishing features of the product.

57-percent-stat

If you think this is bad, think of all the projects that are not even reaching 57% as the average 5.4 subjects involved in the purchasing decision are not agreeing and moving the project forward:

Demand-Gen-2_Forbes

Last Updated on Sunday, 25 December 2016 23:32
 
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Latest Articles

Unit-testing file I/O 26 November 2017, 12.09 Testing
Unit-testing file I/O
Two good news: file I/O is unit-testable, and it is surprisingly easy to do. Let's see how it works! A software no-one asked for First, we need a piece of software that deals with files and that has to be unit-tested. The
Fixing Git pull errors in SourceTree 10 April 2017, 01.44 Software
Fixing Git pull errors in SourceTree
If you encounter the following error when pulling a repository in SourceTree: VirtualAlloc pointer is null, Win32 error 487 it is due to to the Cygwin system failing to allocate a 5 MB large chunk of memory for its heap at
Castle on the hill of crappy audio quality 19 March 2017, 01.53 Audio
Castle on the hill of crappy audio quality
As the yearly dynamic range day is close (March 31st), let's have a look at one of the biggest audio massacres of the year, Ed Sheeran's "Castle on the hill". First time I heard the song, I thought my headphones just got
Necessary evil: testing private methods 29 January 2017, 21.41 Testing
Necessary evil: testing private methods
Some might say that testing private methods should be avoided because it means not testing the contract, that is the interface implemented by the class, but the internal implementation of the class itself. Still, not all
I am right and you are wrong 28 December 2016, 14.23 Web
I am right and you are wrong
Have you ever convinced anyone that disagreed with you about a deeply held belief? Better yet, have you changed your mind lately on an important topic after discussing with someone else that did not share your point of

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