ref(develop): Add selective testing docs

[rbro112]

Adds basic selective testing develop docs.

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PRE-MERGE CHECKLIST

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• Checked Vercel preview for correctness, including links
• PR was reviewed and approved by any necessary SMEs (subject matter experts)
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LEGAL BOILERPLATE

Look, I get it. The entity doing business as "Sentry" was incorporated in the State of Delaware in 2015 as Functional Software, Inc. and is gonna need some rights from me in order to utilize my contributions in this here PR. So here's the deal: I retain all rights, title and interest in and to my contributions, and by keeping this boilerplate intact I confirm that Sentry can use, modify, copy, and redistribute my contributions, under Sentry's choice of terms.

EXTRA RESOURCES

• Sentry Docs contributor guide

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Project	Deployment	Actions	Updated (UTC)
develop-docs	Ready	Preview, Comment	Apr 21, 2026 3:21pm

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
sentry-docs	Ignored	Preview	Apr 21, 2026 3:21pm

[sentry]

Bug: The new documentation file index.tsx has the wrong file extension. It contains MDX content but uses .tsx, so it will be ignored by the documentation build process.
_{Severity: HIGH}

Suggested Fix

Rename the file from develop-docs/backend/testing/index.tsx to develop-docs/backend/testing/index.mdx. This will allow the documentation pipeline to correctly identify and process it as an MDX file.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: develop-docs/backend/testing/index.tsx#L1-L6

Potential issue: The new documentation file `develop-docs/backend/testing/index.tsx`
uses a `.tsx` extension but contains MDX content, including YAML frontmatter. The
documentation generation pipeline, specifically functions in `src/frontmatter.ts` and
`src/mdx.ts`, is configured to only process files with `.md` or `.mdx` extensions. Due
to its `.tsx` extension, this file will be skipped by the pipeline. As a result, the
page will not be included in the static site generation, will be missing from the
sidebar navigation, and will be inaccessible, leading to a 404 error.

[sentry]

Bug: The new documentation file index.msx uses an incorrect extension. The build system only recognizes .md and .mdx files, so this page will not be rendered.
_{Severity: MEDIUM}

Suggested Fix

Rename the file develop-docs/backend/testing/index.msx to develop-docs/backend/testing/index.mdx. Additionally, remove the entry for "develop-docs/backend/testing/index.msx" from the include array in tsconfig.json as it will no longer be necessary.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: tsconfig.json#L83

Potential issue: The pull request introduces a new documentation file
`develop-docs/backend/testing/index.msx` with a non-standard `.msx` extension. The
documentation build system, as seen in `src/frontmatter.ts`, is configured to only
process files with `.md` and `.mdx` extensions. Consequently, the new `.msx` file will
be silently ignored by the build pipeline. This will result in the intended navigation
index page for the backend testing section not being rendered or appearing in the
documentation hierarchy, leading to incomplete documentation. The addition of the file
path to `tsconfig.json` is an incorrect workaround that does not resolve the root issue.

[runningcode]

Suggested change

	Have a paritcularly sensitive PR you want to run all tests on? Add the “Trigger: Override Selective Testing” label and your PR will run all tests.
	Have a particularly sensitive PR you want to run all tests on? Add the “Trigger: Override Selective Testing” label and your PR will run all tests.