Open Source Development Guidelines


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Swedbank Pay is committed to creating a vibrant community around its open source initiative on GitHub and will alongside its partners expose the Swedbank Pay Payment APIs in high quality client modules and libraries. The development of these modules and libraries should be as transparent and accessible to the public as possible. The consequence and meaning of this will be explained in the following chapters of this guideline.

Having the source code, tests, documentation, issues and such all in one place makes the projects governing the modules and libraries easier to grasp and understand for new users. GitHub is the world’s most popular developer and source code hosting platform and offers everything we need in an easy to use package. It is therefore a great choice for hosting the source code for the open source modules and all of their related resources.


For an open source project to become successful, it should follow a few core principles:


Being transparent is one of the most important virtues of an open source project. Being able to inspect the source code, read the documentation, view potentially reported bugs and understand the development process in an accessible and easy to understand way is critical to be able to assert the quality of the project.

Being transparent also makes it apparent that we don’t have anything to hide, underlining our confidence in the quality of what we publish, which of course should be top notch.


An important factor to ensure the quality of any given piece of code is to test it. The test should preferably be automated and be run on every code check-in. The automation can be done through a language-native test framework like NUnit, JUnit or PHPUnit and then have a continuous integration system like Travis or TeamCity execute these tests every time code is pushed to the repository on GitHub.

Code quality of course depends on a lot of other factors too, such as:


The perhaps most important measure of success for an open source project is whether people outside of the project’s core development group contribute to it or not. The contributions can be everything from reported issues to correcting typographic errors in documentation to pull requests for minor or major code contributions.

To be able to attract outside contributors, the project needs to be accessible. While accessibility is an abstract term, it can be broken down into smaller and more concrete parts that are easier to measure and understand.

Is the development process for the project easy to understand? Where are outstanding features listed, who are the developers working on which features and where do they reside? How easy is it to fork the project and make a pull request that has a high chance of being merged?

These are questions that should be asked and that can be answered confidently if the project is managed in a good and orderly fashion. The following list enumerates the most important aspects that a project should be governed by to be perceived as accessible:

  1. Outstanding features and bugs should be easy to find in the list of “issues” in the project’s repository.
  2. The project’s documentation should be easily accessible in or linked to from the project’s README file.
  3. The README file and associated documentation should be written in simple Markdown markup so it is easy to correct by anyone simply by using GitHub’s online Markdown editing features.
  4. How to contribute should be clearly explained in a CONTRIBUTING file.
  5. The process of contributing should be as simple as possible.
    1. The project should follow the norm and best practice of the language and environment it is written in.
    2. There should be tests in the project that are easy to get up and running on a developer machine without installing any external services, tools or libraries, unless they are handled by a package manager like NuGet.
    3. Contributed code should be checked by a continuous integration server that labels the status of pull request accordingly. If a test fails, the contributor should be alerted of its failure through GitHub’s interface.
  6. All code contributions should be run through a public continuous integration server so build failures are visible to the contributor such that it can be fixed without any project manager’s involvement.
  7. The development and branching process should preferably be based on an existing scheme such as GitFlow or GitHub Flow.
  8. All development should be done in public.
    1. Code should be pushed to GitHub regularly, so it’s possible to see progress.
    2. For incomplete features and bugfixes, GitFlow with branch prefixes such as feature/ and hotfix/ should be used
    3. All code in development should be pushed as often as possible.


All source code should be written in a secure way so it avoids the problems enumerated in OWASP Top 10 and SANS 25. It should preferably exist a test for each of these problems such that it is continually verified that the code does not contain any of these problems now or in the future.

No source code should contain secrets, passwords or otherwise sensitive information. If such code is committed by accident, history should be rewritten through interactive rebasing as soon as possible and force-pushed.


All of Swedbank Pay’ open source software should be licensed under a liberal and enterprise, closed source-compatible software license.

The copyright for code written in Swedbank Pay’s open source projects is shared between Swedbank Pay and the individual authors of the source code. This should be stated in the above mentioned LICENSE file as well as in each individual source code file and other metadata (such as .NET assembly information, etc.):

Copyright © Swedbank Pay and Project Contributors

How to Contribute

Contributing details how we ensure that contributors to a project adheres to the rules and principles defined by the project.

Code of Conduct

Every project governed by Swedbank Pay or in its name should have a Code of Conduct.

Release Management

An essential part of any software project is having it released in one form or another so other people can use it. To be able to release software efficiently, several different strategies and methodologies need to exist and be followed. They will be described in the following chapters.


To release software, it needs to be versioned. Swedbank Pay’s open source packages should be versioned according to semantic versioning. This means that whenever backward compatibility is broken, the major version should be incremented. When a new feature is added, the minor version should be incremented and when bug fixes and other minor changes are introduced, the revision number should be incremented.

A version of the software should correspond to a commit in the Git repository. This commit should be tagged with the version number it represents and the commit should be in the branch corresponding with what’s being released; stable code should be in the master branch, while pre-release, alpha or beta code should be in the develop branch or in a release/ prefixed branch.

If a stable version 1.2.5 of a project is to be released, the commit representing that version should be tagged in Git with the value 1.2.5 and the commit should exist in the master branch.

To help with automating versioning in .NET based projects, GitVersion can be used. For most uses, GitVersionTask performs the job perfectly. It understands GitFlow and increments the version number automatically based on which branch the code being built exists on.

Branching strategy

To make versioning easier, the Git repository should follow GitFlow, GitHub Flow or derivates, so released and stable code is kept in the master branch, while unstable and pre-released code — if such is required — is kept in the develop branch.

While they can be considered optional since all ongoing development can be done directly in the develop branch; features, hotfixes and such should preferably be done in separate branches using the GitFlow-standard branch prefixes feature, hotfix/, etc.


Software written for an environment that has a marketplace or other official storefront for applications (or “modules”, “extensions” and what have you) such as Apple’s App Store or Google Play, should try to publish the released software in these marketplaces.

Releases should correspond to a tagged version number and a Release for the version should be created on GitHub. The GitHub Release should summarize all changes made since the last release and highlight new features, possibly by referring to blog entries or similar that describes them in more detail.

To help with writing release notes, projects can use the tool GitReleaseNotes.