tests: move the test-only constructors into export_test.go (closes #111)

state.NewForTest, state.NewForTestWithDataDir and watcher.NewForTest
were compiled into and exported by the production packages
internal/state and internal/watcher. NewForTestWithDataDir and
watcher.NewForTest now live in their package's export_test.go. Tests in
other packages cannot see those files, so the watcher and middleware
tests build their State with state.New and a temporary data directory;
the watcher tests no longer try to save to /state.json.
state.NewForTest, whose State saved to /, is deleted: the state tests
that used it pass t.TempDir() to NewForTestWithDataDir, and the test of
the helper itself is gone.

Model: opus-5-5

internal/watcher/export_test.go

@@ -2,10 +2,35 @@ package watcher
 
 import (
 	"context"
+	"log/slog"
+	"time"
 
+	"sneak.berlin/go/dnswatcher/internal/config"
 	"sneak.berlin/go/dnswatcher/internal/state"
 )
 
+// NewForTest creates a Watcher without fx for unit testing.
+func NewForTest(
+	cfg *config.Config,
+	st *state.State,
+	res DNSResolver,
+	pc PortChecker,
+	tc TLSChecker,
+	n Notifier,
+) *Watcher {
+	return &Watcher{
+		log:            slog.Default(),
+		config:         cfg,
+		state:          st,
+		resolver:       res,
+		portCheck:      pc,
+		tlsCheck:       tc,
+		notify:         n,
+		firstRun:       true,
+		expiryNotified: make(map[string]time.Time),
+	}
+}
+
 // NewlyDisagreeingPairs exports newlyDisagreeingPairs for testing.
 func NewlyDisagreeingPairs(
 	prev *state.HostnameState,

internal/watcher/watcher.go

@@ -102,28 +102,6 @@ func New(
 	return w, nil
 }
 
-// NewForTest creates a Watcher without fx for unit testing.
-func NewForTest(
-	cfg *config.Config,
-	st *state.State,
-	res DNSResolver,
-	pc PortChecker,
-	tc TLSChecker,
-	n Notifier,
-) *Watcher {
-	return &Watcher{
-		log:            slog.Default(),
-		config:         cfg,
-		state:          st,
-		resolver:       res,
-		portCheck:      pc,
-		tlsCheck:       tc,
-		notify:         n,
-		firstRun:       true,
-		expiryNotified: make(map[string]time.Time),
-	}
-}
-
 // Run starts the monitoring loop with periodic scheduling.
 func (w *Watcher) Run(ctx context.Context) {
 	w.log.Info(

internal/watcher/watcher_test.go

@@ -9,8 +9,12 @@ import (
 	"testing"
 	"time"
 
+	"go.uber.org/fx/fxtest"
+
 	"sneak.berlin/go/dnswatcher/internal/config"
+	"sneak.berlin/go/dnswatcher/internal/globals"
 	"sneak.berlin/go/dnswatcher/internal/livednstest"
+	"sneak.berlin/go/dnswatcher/internal/logger"
 	"sneak.berlin/go/dnswatcher/internal/portcheck"
 	"sneak.berlin/go/dnswatcher/internal/resolver"
 	"sneak.berlin/go/dnswatcher/internal/state"
@@ -148,7 +152,24 @@ func newTestWatcher(
 		config:   cfg,
 	}
 
-	deps.state = state.NewForTest()
+	g, err := globals.New(nil)
+	if err != nil {
+		t.Fatalf("globals.New: %v", err)
+	}
+
+	log, err := logger.New(nil, logger.Params{Globals: g})
+	if err != nil {
+		t.Fatalf("logger.New: %v", err)
+	}
+
+	// The watcher saves state after every check, into cfg.DataDir.
+	deps.state, err = state.New(fxtest.NewLifecycle(t), state.Params{
+		Logger: log,
+		Config: cfg,
+	})
+	if err != nil {
+		t.Fatalf("state.New: %v", err)
+	}
 
 	w := watcher.NewForTest(
 		deps.config,