Trying to understand what Travis CI does and when it should be used

Question

I am very new to Git and I am planning to contribute to some open-source project on GitHub after discovering a small error in it. Upon forking it and fixing the error, I purposed a pull request and I noticed this showing up:

Failed — The Travis CI build failed

Looking into the details I discovered it was caused by Could not find .travis.yml, which made perfect sense since I had not signed in to Travis Cl with and add .travis.yml to the repository.

This is my first time hearing about Travis and what that is known as continuous integration. And it sounds pretty cool so in order to learn more about it, I looked it up on Wikipedia.

Travis CI is a hosted, distributed continuous integration service used to build and test projects hosted at GitHub. Travis CI automatically detects when a commit has been made and pushed to a GitHub repository that is using Travis CI, and each time this happens, it will try to build the project and run tests. This includes commits to all branches, not just to the master branch.

My current understanding of Travis CI is that what it does is automatically pushing the project upon git commit -am ".." and I don't quite understand some part of it.

1. By building the project and run tests, what tests is it going to run? And how is it going to "build" the project? (like compiling it to binary?)

2. It states that "This includes commits to all branches" - but what if I don't want to commit to all branches?

3. Is it alright if I don't use Travis Cl at all? Under what circumstances is it best to use it (or it must be used)?

Headstream

Answer 1

The simplest way to explain Travis CI is that it runs your program's tests every time you commit to GitHub (this can be configured in many ways, and you can always disable builds on some branches). The point of this is that you can often discover very quickly if your commit broke something, and fix it before it becomes a problem. I would recommend running Travis CI on every GitHub repo that you have unit tests in and is using a programming language supported by Travis CI. Since setting up Travis CI is very easy, I don't normally see a good reason not to use it, unless you don't care if you have passing tests in your program or not. Feel free to leave a comment if you have any more questions. You can read more about Travis CI here.

Daina

It says it's "free" for open source projects, but says your first 100 builds are free. So... it's not free then? Even developing alone I could get to 100 builds very quickly. Am I reading this wrong? Can't find any info anywhere. @Daina – Annihilation

It's always free for open source projects. For private repos, you get 100 free builds before you need to sign up for a paid plan. – Daina

Isnt the typical git workflow pulling the most recent commit and merging locally and testing and then pushing to remote? – Pazia

What about people who do web development with cli tools for Angular, React, or Vue? The frameworks provide instant transpiling and testing feedback when running dev server. Is there any difference between that and Travis CI, or should I say between running unit tests before committing and using CI in general? – Spidery

So travis doesn't makes sense, I can easily drop travis by using git commit hooks and block pushes that return errors from the test command. – Expunge

Just want to point out that this @Daina person was working at Travis when they made this answer, which very much sounds like very biased marketing promotion, on this website which is meant to share objective and neutral answers.... Travis is a proprietary and non-free CI solution. There are a lot of alternatives, several free and open-source. – Braiding

Answer 2

As you have already discovered what is Travis-CI, I would directly point to the questions you have.

By building the project and run tests, what tests is it going to run? And how is it going to "build" the project? (like compiling it to binary?)

In the .travis.yml a file you're specifying your OS, the programming language, your repo branch, the project file name and other details. By reading this file, Travis-CI will use the specific compilers which installed on their server to compile our code. Probably they will have the same mechanism as we have for Github. For the first time, they might pull the code [if we have specified specific branches they might pull the code from those branches only]. Also, we have authenticated to use our account with Travis-CI, whenever we make a commit, there should be some notification should fire to Travis-CI server thus it will be recognized as a commit and it will start compiling.

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It states that "This includes commits to all branches" - but what if I don't want to commit to all branches?

You can specify different branches or the master branch. And it should only compile the specific branches specified in .travis.yml file.

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Is it alright if I don't use Travis Cl at all? Under what circumstances is it best to use it (or it must be used)?

Yes, it's alright. Not a big deal. But what benefits you will be missing by not using this easy to integrate engine with your repo. Everytime you commit it may possible that it miss something and it couldn't compile because of a code. How will you know? Thus, you should use Travis-CI.

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_{I have written a blog post which you can read to know, what is Travis-CI, Continuous Integrations and how to linked Travis-CI with your Github Repo. I have written it for a Swift repository.}

Titty

Answer 3

I think am in a very good position to answer you question as am currently learning Travis CI at the moment. The first problem you encountered in the first place is because the project you are contributing to is using Travis CI to test and build the project. If the project isn't using Travis CI, you wouldn't have come across such error.

The solution is checkout Travis CI website and learn how it work and how it affected the project you are working on. This will put you in a very good position to understand what's failing in your code and how to fix it.

To answer the first question about building the project.

By building the project and run tests, what tests is it going to run? And how is it going to "build" the project? (like compiling it to binary?)

It's means how the source code is processed before use/test. It depends on the language you are writing. For example, if the project is writing with PHP. It's not going to build my code into executable file like C/C++ source code. It will run my PHP code on PHP interpreter and test it as it does so. It still goes through the normal compiling process your preferred language goes through.

Scrophulariaceous