test(mergeQueue): pin errorMessage's null-rejection guards, the once-per-run warning's initial state and the [bot] suffix anchor

__tests__/utils/mergeQueueGuards.test.ts

@@ -0,0 +1,63 @@
+import type { Octokit } from '@octokit/rest'
+
+import { afterEach, describe, expect, it, vi } from 'vitest'
+
+import { enqueue, enqueuedByBot, queueState } from '../../src/utils/mergeQueue'
+import pullReqOpenedEvent from '../fixtures/pullReq/pullReqOpenedEvent.json'
+
+import * as utils from '../testUtils'
+
+// Guards of src/utils/mergeQueue.ts that line coverage reaches but that no test
+// in mergeQueue.test.ts would notice changing. This file deliberately does not
+// call setupActionsEnv() or resetMergeQueueWarnings(): the once-per-run warning
+// is pinned on a module instance nothing has reset.
+
+const context = new utils.MockContext(pullReqOpenedEvent)
+const state = { pullRequestId: 'PR_kwDOtest', headOid: 'headsha', enabled: true, inQueue: false }
+
+function rejectingWith(reason: unknown): Octokit {
+  return { graphql: vi.fn().mockRejectedValue(reason) } as unknown as Octokit
+}
+
+afterEach(() => vi.resetModules())
+
+describe('errorMessage', () => {
+  it('reports a null rejection of the state query as "null" instead of throwing', async () => {
+    const core = await import('@actions/core')
+
+    await expect(queueState(rejectingWith(null), context, 7)).resolves.toBeUndefined()
+
+    expect(core.warning).toHaveBeenCalledWith('could not read the merge queue state of pr #7; falling back to a direct merge: null')
+  })
+
+  it('classifies an undefined rejection of the enqueue mutation as other with the message "undefined"', async () => {
+    await expect(enqueue(rejectingWith(undefined), context, state, 'headsha')).resolves.toEqual({ ok: false, message: 'undefined', kind: 'other' })
+  })
+
+  it('does not treat an errors property that is not an array as GraphQL errors', async () => {
+    await expect(enqueue(rejectingWith({ errors: 'not an array' }), context, state, 'headsha')).resolves.toEqual({ ok: false, message: '[object Object]', kind: 'other' })
+  })
+})
+
+describe('queueState warning', () => {
+  it('warns on the first failure of a run without any reset having happened', async () => {
+    const [core, fresh] = await Promise.all([import('@actions/core'), import('../../src/utils/mergeQueue')])
+    vi.mocked(core.warning).mockClear()
+
+    await expect(fresh.queueState(rejectingWith(new Error('first failure')), context, 7)).resolves.toBeUndefined()
+    await expect(fresh.queueState(rejectingWith(new Error('second failure')), context, 8)).resolves.toBeUndefined()
+
+    expect(core.warning).toHaveBeenCalledTimes(1)
+    expect(core.warning).toHaveBeenCalledWith(expect.stringContaining('pr #7; falling back to a direct merge: first failure'))
+  })
+})
+
+describe('enqueuedByBot', () => {
+  it.each([
+    ['dependabot[bot]-fan', false],
+    ['[bot]renovate', false],
+    ['github-actions[bot]', true],
+  ])('%s -> %s: [bot] counts only as a suffix', (login, expected) => {
+    expect(enqueuedByBot({ state: 'QUEUED', position: 1, enqueuer: login })).toBe(expected)
+  })
+})