add test

test/issue-3959.js

@@ -0,0 +1,55 @@
+const { describe, test } = require('node:test')
+const assert = require('node:assert')
+const { createServer } = require('node:http')
+const MemoryCacheStore = require('../lib/cache/memory-cache-store.js')
+const { request, Agent, setGlobalDispatcher } = require('..')
+const { interceptors } = require('..')
+
+describe('Cache with Vary headers', () => {
+  test('should cache response when Vary header exists but request header is missing', async () => {
+    let requestCount = 0
+    const server = createServer((req, res) => {
+      requestCount++
+      res.setHeader('Vary', 'Accept-Encoding')
+      res.setHeader('Cache-Control', 'max-age=60')
+      res.end(`Request count: ${requestCount}`)
+    })
+
+    await new Promise(resolve => server.listen(0, resolve))
+    const port = server.address().port
+    const url = `http://localhost:${port}`
+
+    const store = new MemoryCacheStore()
+    const agent = new Agent()
+    setGlobalDispatcher(
+      agent.compose(
+        interceptors.cache({
+          store,
+          cacheByDefault: 1000,
+          methods: ['GET']
+        })
+      )
+    )
+
+    const res1 = await request(url)
+    const body1 = await res1.body.text()
+    assert.strictEqual(body1, 'Request count: 1')
+    assert.strictEqual(requestCount, 1)
+
+    const res2 = await request(url)
+    const body2 = await res2.body.text()
+    assert.strictEqual(body2, 'Request count: 1')
+    assert.strictEqual(requestCount, 1)
+
+    const res3 = await request(url, {
+      headers: {
+        'Accept-Encoding': 'gzip'
+      }
+    })
+    const body3 = await res3.body.text()
+    assert.strictEqual(body3, 'Request count: 2')
+    assert.strictEqual(requestCount, 2)
+
+    await new Promise(resolve => server.close(resolve))
+  })
+})