Test shutdown exit codes, Sentry startup failure and the processing wait (closes #86)

These tests fail until the change that follows: runApp and
WaitForProcessing do not exist yet, the server has no shutdowner, and a
Sentry DSN that cannot be used exits the process from a goroutine
instead of failing the server's start hook.

runApp must return the exit code a shutdown request carries, 0 without
one, and 1 when the app fails to start or stop. A listen error must ask
fx to shut down with exit code 1. WaitForProcessing must wait for an
image being processed and report it when its context ends first.

Model: opus-5-5

internal/server/shutdown_internal_test.go

@@ -0,0 +1,96 @@
+package server
+
+import (
+	"log/slog"
+	"net"
+	"testing"
+	"time"
+
+	"go.uber.org/fx"
+	"go.uber.org/fx/fxtest"
+
+	"sneak.berlin/go/pixa/internal/config"
+	"sneak.berlin/go/pixa/internal/globals"
+	"sneak.berlin/go/pixa/internal/logger"
+)
+
+// shutdownRecorder is an fx.Shutdowner that sends the options of each
+// shutdown request on requests.
+type shutdownRecorder struct {
+	requests chan []fx.ShutdownOption
+}
+
+func (r shutdownRecorder) Shutdown(opts ...fx.ShutdownOption) error {
+	r.requests <- opts
+
+	return nil
+}
+
+// TestSentryInitFailureFailsStartup checks that a Sentry DSN that cannot be
+// used makes the server's start hook fail, so fx stops what has already
+// started, instead of the process exiting from a goroutine.
+func TestSentryInitFailureFailsStartup(t *testing.T) {
+	t.Parallel()
+
+	lc := fxtest.NewLifecycle(t)
+
+	log, err := logger.New(lc, logger.Params{Globals: &globals.Globals{}})
+	if err != nil {
+		t.Fatalf("logger.New() error = %v", err)
+	}
+
+	_, err = New(lc, Params{
+		Logger:  log,
+		Globals: &globals.Globals{Appname: "pixad"},
+		Config:  &config.Config{SentryDSN: "not-a-dsn"},
+	})
+	if err != nil {
+		t.Fatalf("New() error = %v", err)
+	}
+
+	err = lc.Start(t.Context())
+	t.Logf("Start() error = %v", err)
+
+	if err == nil {
+		t.Fatal("Start() error = nil, want the Sentry initialization error")
+	}
+}
+
+// TestListenErrorRequestsShutdownWithExitCode1 occupies the server's port
+// and checks that the listen error asks fx to shut down with exit code 1.
+func TestListenErrorRequestsShutdownWithExitCode1(t *testing.T) {
+	t.Parallel()
+
+	busy, err := (&net.ListenConfig{}).Listen(t.Context(), "tcp", ":0")
+	if err != nil {
+		t.Fatalf("Listen() error = %v", err)
+	}
+
+	t.Cleanup(func() { _ = busy.Close() })
+
+	addr, ok := busy.Addr().(*net.TCPAddr)
+	if !ok {
+		t.Fatalf("listener address %v is not a TCP address", busy.Addr())
+	}
+
+	requests := make(chan []fx.ShutdownOption, 1)
+	s := &Server{
+		log:        slog.New(slog.DiscardHandler),
+		config:     &config.Config{Port: addr.Port},
+		shutdowner: shutdownRecorder{requests: requests},
+	}
+	s.httpServer = s.newHTTPServer()
+
+	go s.serveUntilShutdown()
+
+	select {
+	case opts := <-requests:
+		t.Logf("shutdown options = %v", opts)
+
+		if len(opts) != 1 || opts[0] != fx.ExitCode(1) {
+			t.Errorf("shutdown options = %v, want [fx.ExitCode(1)]", opts)
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatal("no shutdown was requested after the listen error")
+	}
+}