test: add watcher orchestrator tests with mock dependencies

Tests cover: first-run baseline, NS change detection, record change
detection, port state changes, TLS expiry warnings, graceful shutdown,
and NS failure/recovery scenarios.

internal/watcher/interfaces.go

@@ -0,0 +1,60 @@
+// Package watcher provides the main monitoring orchestrator.
+package watcher
+
+import (
+	"context"
+
+	"sneak.berlin/go/dnswatcher/internal/tlscheck"
+)
+
+// DNSResolver performs iterative DNS resolution.
+type DNSResolver interface {
+	// LookupNS discovers authoritative nameservers for a domain.
+	LookupNS(
+		ctx context.Context,
+		domain string,
+	) ([]string, error)
+
+	// LookupAllRecords queries all record types for a hostname,
+	// returning results keyed by nameserver then record type.
+	LookupAllRecords(
+		ctx context.Context,
+		hostname string,
+	) (map[string]map[string][]string, error)
+
+	// ResolveIPAddresses resolves a hostname to all IP addresses.
+	ResolveIPAddresses(
+		ctx context.Context,
+		hostname string,
+	) ([]string, error)
+}
+
+// PortChecker tests TCP port connectivity.
+type PortChecker interface {
+	// CheckPort tests TCP connectivity to an address and port.
+	CheckPort(
+		ctx context.Context,
+		address string,
+		port int,
+	) (bool, error)
+}
+
+// TLSChecker inspects TLS certificates.
+type TLSChecker interface {
+	// CheckCertificate connects via TLS and returns cert info.
+	CheckCertificate(
+		ctx context.Context,
+		ip string,
+		hostname string,
+	) (*tlscheck.CertificateInfo, error)
+}
+
+// Notifier delivers notifications to configured endpoints.
+type Notifier interface {
+	// SendNotification sends a notification with the given
+	// details.
+	SendNotification(
+		ctx context.Context,
+		title, message, priority string,
+	)
+}