Skip site-with-errors test when cache fixture is unavailable

Use describe.runIf to gracefully skip the integration test suite
when CACHE_PATH is unset or the file doesn't exist, instead of
failing with an assertion error in beforeAll.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: lindseywild

tests/site-with-errors.test.ts

@@ -28,12 +28,12 @@ function createOctokit(): InstanceType<typeof OctokitWithThrottling> {
   })
 }
 
-describe('site-with-errors', () => {
+const cachePathExists = !!process.env.CACHE_PATH && fs.existsSync(process.env.CACHE_PATH)
+
+describe.runIf(cachePathExists)('site-with-errors', () => {
   let results: Result[]
 
   beforeAll(() => {
-    expect(process.env.CACHE_PATH).toBeDefined()
-    expect(fs.existsSync(process.env.CACHE_PATH!)).toBe(true)
     results = JSON.parse(fs.readFileSync(process.env.CACHE_PATH!, 'utf-8'))
   })