Migrated test/unit/api bucket to vitest

[9larsons]

Summary

Continues the vitest migration (after #27898 / #27900 / #27974) by moving the test/unit/api bucket — 33 files, 280 tests — from mocha to vitest.

What's changed

• vitest.config.ts — added test/unit/api/** to test.include
• package.json — removed ./test/unit/api from test:unit:base so vitest is the sole runner
• members.test.js — before() → beforeAll()
• serializers/input/pages.test.js + serializers/input/posts.test.js — four this.timeout(N) calls → the it(name, {timeout: N}, fn) options form
• validators/input/pages.test.js + validators/input/posts.test.js — see below

Unhandled-rejection fix

validators/input/{pages,posts}.test.js had a beforeEach that stubbed Member.findPage with .returns(Promise.reject()). That eagerly creates a rejected promise at stub-setup time. When a test never exercises the stub, the promise is never consumed and Node flags it as an unhandled rejection — 60 of them across the two files ({ type: 'Unhandled Rejection', message: undefined }). Mocha silently ignored these; vitest surfaces them and fails the run.

Fix: switched to sinon's lazy .rejects() / .resolves(), which only create the promise when the stub is actually called.

Test plan

• pnpm test:vitest test/unit/api (from ghost/core): 33 files / 280 tests pass, zero unhandled rejections
• pnpm test:unit:base (mocha): 5386 tests pass
• pnpm exec eslint clean for changed files
• CI green

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between c549856 and e423f5c.

📒 Files selected for processing (7)

• ghost/core/package.json
• ghost/core/test/unit/api/canary/utils/serializers/input/pages.test.js
• ghost/core/test/unit/api/canary/utils/serializers/input/posts.test.js
• ghost/core/test/unit/api/canary/utils/validators/input/pages.test.js
• ghost/core/test/unit/api/canary/utils/validators/input/posts.test.js
• ghost/core/test/unit/api/endpoints/members.test.js
• ghost/core/vitest.config.ts

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Walkthrough

This PR migrates the test/unit/api test suite from Mocha to Vitest. The core changes remove ./test/unit/api from the Mocha test:unit:base script in package.json and add test/unit/api/**/*.test.{js,ts} to Vitest's test.include configuration. Test files are updated for Vitest compatibility: timeout declarations move from this.timeout(X) calls inside test bodies to it(..., { timeout: X }) options, before() hooks change to beforeAll(), and Sinon stub patterns switch from manually returning promises to using .rejects() and .resolves() helpers.

Possibly related PRs

• TryGhost/Ghost#27901: Introduces a new CI pnpm test:vitest step that directly depends on the vitest.config.ts changes in this PR to run the newly migrated test/unit/api tests.
• TryGhost/Ghost#27900: Adjusts the same test runner configuration buckets in package.json and vitest.config.ts to rebalance test suite distribution between Mocha and Vitest.
• TryGhost/Ghost#27898: Modifies vitest.config.ts test.include globs to affect which unit tests run under Vitest, using the same configuration pattern as this PR.

Suggested reviewers

• EvanHahn

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Linked Issues check	⚠️ Warning	The pull request objective regarding Vitest migration is unrelated to the linked issue #39 about image upload markdown functionality; no coding-related requirements from issue #39 are addressed.	The pull request addresses Vitest migration but does not implement any requirements from the linked issue #39. Verify that issue #39 requirements are intentionally excluded or link the appropriate issue that describes the Vitest migration work.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main objective of the pull request: migrating the test/unit/api bucket from Mocha to Vitest.
Description check	✅ Passed	The description thoroughly explains the changes, including what was migrated, how Mocha-specific APIs were converted, and documents the unhandled-rejection fix that was necessary for Vitest compatibility.
Out of Scope Changes check	✅ Passed	All changes in the pull request are directly related to the Vitest migration objective: configuration updates, Mocha-to-Vitest API conversions, and unhandled-rejection fixes. No unrelated changes are present.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch vitest-migrate-api-bucket

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