The smallest Azure DevOps website you can make that will test and build an Azure App Services Web App

1. The entire "application" rendering "Hello World" to this web server's homepage is in the 16 lines of code in /src/web/server.js.
2. The suite of "build-time unit tests" confirming that the homepage does indeed say "Hello World!" in the 22 lines of code in /src/__tests__/my-first-test.js.
3. The Azure DevOps Pipeline configuration file is in the 64 lines of code in /cicd/my-azure-build-pipeline.yml. This is the magic codebase that:
   • Refuses to "build" a new server-ready runtime if the unit tests fail. (e.g. if some Beatles-fan QA changed line 12 of /src/__tests__/my-first-test.js to expect the homepage to say "Hello Goodbye" instead).
   • Builds a server-ready runtime and prepares it for deployment to an actual server if the unit tests pass.
   • Makes sure the unit test results show up beautifully displayed in red and green within the Azure DevOps -> Test Plans -> Runs dashboard.
4. (The details of how exactly the Pipeline knows what "testing" and "building" look like are in the 38 lines of code at /package.json, but the contents of this file are really cryptic if you're not an experienced web developer and not terribly important to understanding the magic of the codebase.)

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My apologies for the unconventional folder structure -- when I'm trying to figure out tooling around a codebase, I like to be sure I'm giving things "non-magic" filepaths.

Anyway, once I clone this repo into an Azure DevOps repo and click Pipelines -> Pipelines -> New Pipeline -> Azure Repos Git -> (the name of my ADO repo) -> Existing Azure Pipelines YAML file -> Path of /cicd/my-azure-build-pipeline.yml -> Continue and run it...

...I see that it outputs an artifact with the following file structure:

MyBuiltWebsite/
├─ node_modules/
│  └─ ...
└─ server.js

Then under Pipelines in left-nav, I click Releases and in the middle click the New picklist and its New release pipeline option.

I close the Select a template flyout at right, and in the left-hand side of the release pipeline GUI design area, in the Artifacts box, I click Add.

I leave the Source type icon set to Build and leave Project set to (the name of my ADO project). I change Source (build pipeline) to (the name of my ADO repo). I leave Default version on Latest. I change Source alias from something like (_the name of my ADO repo) to MyBuiltWebsite.

In the left-hand side of the release pipeline GUI design area, in the Stages box, click Add and then New stage.

In the Select a template flyout at right, I choose Deploy a Node.js app to Azure App Service and click Apply.

I rename Stage name to something like My arbitrary stage name, then at left click on the 1 job, 1 task link.

In the My arbitrary stage name task up top, I drop down Azure subscription and set it to the one showing up under Available Azure service connections (which I'd already set up earlier by choosing the one under Available Azure Subscriptions, dropping down the Authorize extended picklist, clicking Advanced options, leaving it on Service Principal Authentication, setting the Resource Group to the same one that I'd already created an F1 Linux Azure App Service Plan resource and an Azure Web App resource in, clicking the Allow all pipelines to use this connection checkbox, and clicking OK). I also change App type to Web App on Linux, pick the Azure Web App I'd already created out of the App Service Name dropdown, and set Startup command to node ./server.js.

In the Run on agent slightly indented task below that, I change the Agent pool to Azure Pipelines and the Agent Specification to ubuntu-latest.

In the Deploy Azure App Service slightly indented task at bottom, I change Package or folder to $(System.DefaultWorkingDirectory)/MyBuiltWebsite/MyBuiltWebsite, which I can see with the ... button has this file structure:

Linked artifacts/
├─ MyBuiltWebsite (Build)/
│  ├─ MyBuiltWebsite/
│  │  ├─ node_modules/
│  │  │  └─ ...
│  │  └─ server.js

I also change Runtime Stack to 18 LTS (Node|18-lts) and make sure Startup command says node ./server.js.

Then I click Create release in the upper right and watch the logs.

The Deploy Azure App Service log claims to have "Successfully deployed web package to App Service", but when I visit http://my-app-service-name.azurewebsites.net, it takes forever and finally 504-errors out.

---

Thanks Donald for troubleshooting that the server.js script needs to be const port = (process.env.PORT || 3000); not const port = 3000; and that the Settings -> Configuration for the Azure web app resource needed an extra application setting added to it with a Name of PORT and a Value of 3000 (configurable by appending -PORT 3000 to App settings under the Deploy Azure App Service task of the release pipeline as an alternative, but actually not needed at all -- fine to just let Azure App Service Web App resource pick a random port at its leisure and implicitly set PORT now that we have const port = (process.env.PORT || 3000); in place. I deleted the extra application setting and tried, and confirmed it to be the case that nothing in all of Azure config needs to think about a number 3000 at all -- that can just be a handy thing for testing on my local machine).

Docs:

Your Node.js app needs to listen to the right port to receive incoming requests. App Service sets the environment variable PORT in the Node.js container, and forwards the incoming requests to your container at that port number. To receive the requests, your app should listen to that port using process.env.PORT.

My site is live on the internet now!

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New and improved: now with a more standard-looking npm run tests + npm run build-looking CI/CD pipeline and with build-time unit test results that appear in Azure DevOps's "Test Plans -> Runs" portal!