test(serve): shutdown waits for in-flight requests and the worker, bounded (#50), red

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

cmd/tapir/shutdown_test.go

@@ -2,6 +2,8 @@ package main
 
 import (
 	"context"
+	"net/http"
+	"net/http/httptest"
 	"os"
 	"syscall"
 	"testing"
@@ -28,3 +30,64 @@ func TestShutdownContext_IsCancelledBySIGTERMAndSIGINT(t *testing.T) {
 		})
 	}
 }
+
+// serveHTTP must not return while a request is in flight or the worker is still recording
+// its job: ListenAndServe returns ErrServerClosed the moment Shutdown starts, so returning
+// from it let the process exit before either finished (#50).
+func TestServeHTTP_ReturnsOnlyAfterTheInFlightRequestAndTheWorkerHaveFinished(t *testing.T) {
+	release := make(chan struct{})
+	entered := make(chan struct{})
+	srv := httptest.NewUnstartedServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		close(entered)
+		<-release
+		_, _ = w.Write([]byte("ok"))
+	}))
+	srv.Start()
+	defer srv.Close()
+	ctx, cancel := context.WithCancel(context.Background())
+	workerDone := make(chan struct{})
+	returned := make(chan error, 1)
+	go func() { returned <- serveHTTP(ctx, srv.Config, srv.Listener, nil, workerDone, 5*time.Second) }()
+
+	go func() { _, _ = http.Get(srv.URL) }()
+	<-entered
+	cancel()
+
+	assertPending := func(why string) {
+		t.Helper()
+		select {
+		case err := <-returned:
+			t.Fatalf("serveHTTP returned (%v) %s", err, why)
+		case <-time.After(150 * time.Millisecond):
+		}
+	}
+	assertPending("while a request was still in flight")
+	close(release)
+	assertPending("before the worker finished")
+	close(workerDone)
+	select {
+	case err := <-returned:
+		if err != nil {
+			t.Fatalf("serveHTTP: %v", err)
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("serveHTTP did not return once the request and the worker had finished")
+	}
+}
+
+func TestServeHTTP_GivesUpOnAWorkerThatNeverFinishesAfterTheGrace(t *testing.T) {
+	srv := httptest.NewUnstartedServer(http.NotFoundHandler())
+	srv.Start()
+	defer srv.Close()
+	ctx, cancel := context.WithCancel(context.Background())
+	returned := make(chan error, 1)
+	go func() { returned <- serveHTTP(ctx, srv.Config, srv.Listener, nil, make(chan struct{}), 200*time.Millisecond) }()
+
+	cancel()
+
+	select {
+	case <-returned:
+	case <-time.After(3 * time.Second):
+		t.Fatal("a stuck worker must not hold the process past the grace period")
+	}
+}