test(koa-router): add test using router prefix

tests/versioned/koa-router.tap.js

@@ -465,10 +465,10 @@ tap.test('koa-router instrumentation', (t) => {
 
     const nestedRouter = new Router()
     nestedRouter.get('/:second', function terminalMiddleware(ctx) {
-      ctx.body = 'want this to set the name'
+      ctx.body = 'this is a test'
     })
     nestedRouter.get('/second', function secondMiddleware(ctx) {
-      ctx.body = 'this is a test'
+      ctx.body = 'want this to set the name'
     })
     router.use('/:first', nestedRouter.routes())
     app.use(router.routes())
@@ -499,6 +499,48 @@ tap.test('koa-router instrumentation', (t) => {
     run('/123/second')
   })
 
+  t.test('app-level middleware should not rename tx from prefixed router', (t) => {
+    app.use(function appLevelMiddleware(ctx, next) {
+      return next().then(() => {
+        ctx.body = 'do not want this to set the name'
+      })
+    })
+
+    router.get('/:second', function terminalMiddleware(ctx) {
+      ctx.body = 'this is a test'
+    })
+    router.get('/second', function secondMiddleware(ctx) {
+      ctx.body = 'want this to set the name'
+    })
+    router.prefix('/:first')
+    app.use(router.routes())
+
+    helper.agent.on('transactionFinished', (tx) => {
+      t.exactSegments(
+        tx.trace.root, [{
+          name: 'WebTransaction/WebFrameworkUri/Koa/GET//:first/second',
+          children: [{
+            name: 'Nodejs/Middleware/Koa/appLevelMiddleware',
+            children: [{
+              name: 'Koa/Router: /',
+              children: [{
+                name: 'Nodejs/Middleware/Koa/terminalMiddleware//:first/:second'
+              }]
+            }]
+          }]
+        }],
+        'should have expected segments'
+      )
+      t.equal(
+        tx.name,
+        'WebTransaction/WebFrameworkUri/Koa/GET//:first/second',
+        'should be named after the middleware responsible for originally responding'
+      )
+      t.end()
+    })
+    run('/123/second')
+  })
+
   t.autoend()
 
   function run(path) {