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The Key Principles of Continuous Delivery

In the seminal book Accelerate, Forsgren and her co-authors provide empirical evidence that Continuous Delivery has a positive impact on the performance of software development organisations. If organisations neglect some of the principles and practices of Continuous Delivery, their performance will suffer. They will reach the point where simple changes will take ages to implement. Not so with Continuous Delivery.

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Creating A Custom Yocto Layer

After having built the reference Linux image from a SoM, SoC or terminal maker and having run it on the board, we must inevitably custom-tailor this image to our needs. We must create our own Yocto layer. We must remove all the unnecessary packages and make our core application start automatically on power-up. Here is a step-by-step guide how to turn the application layer for a Toradex Verdin iMX8M Plus board into our own custom layer. The guide should also work for other boards.

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Installing Linux Images on Toradex Verdin Boards

In the post Setting Up Yocto Projects with kas, we built the Linux image for the Toradex Verdin iMX8M Plus. It’s time to flash the image on the board using the Toradex Easy Installer (TEZI). It’s a three-step procedure: wire up the board in a special way, install and run TEZI on the board, and flash our custom-built Linux image from a USB drive on the board.

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Parking at Munich Airport: An Awful Experience

The parking experience at Munich Airport is awful. It is too easy to do something wrong, which can only be remedied by calling support. The bad user experience is caused by a bad system architecture. The pieces for a better architecture are already in place. Improving the interaction between these pieces improves the architecture and a fortiori the user experience. I can at least dream of a better parking experience in the future, although I can’t change the current one.

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Can We Use Trunk-Based Development for Legacy Software?

Not right away! Trunk-Based Development requires that the software builds and passes enough tests, before we integrate our changes into the main branch (a.k.a., trunk). We have enough tests, if breaking the software is highly unlikely. By definition, legacy code has no or not enough tests. Hence, we cannot apply trunk-based development right way, but should evolve our development process towards it.

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Applying TDD to Classes Accessing Files

We start with unit tests reading a file line by line with QFile. Unit tests accessing the file system are not considered unit tests, as they may be slow and may depend on each other in surprising ways (see A Set of Unit Testing Rules by Michael Feathers). In a first step, we encapsulate QFile in a class TextFile and provide a fake implementation representing the file as a list of strings kept in main memory. In a second step, we introduce an interface, from which the product and fake implementations derive. We can now apply TDD to classes accessing files.

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