M3: add unit tests for config resolution and cryptsetup helpers

Tests cover: alias resolution (exact match, device path match, unknown,
empty methods default), AliasFor lookup, Load with missing/valid YAML,
MapperName generation, and token plugin directory detection.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/config/config_test.go

@@ -0,0 +1,128 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestResolveDevice_ExactAlias(t *testing.T) {
+	cfg := &Config{
+		Devices: map[string]DeviceConfig{
+			"backup": {UUID: "abc-123", Methods: []string{"fido2", "passphrase"}},
+		},
+	}
+	r := cfg.ResolveDevice("backup")
+	if r.UUID != "abc-123" {
+		t.Errorf("UUID = %q, want %q", r.UUID, "abc-123")
+	}
+	if len(r.Methods) != 2 || r.Methods[0] != "fido2" {
+		t.Errorf("Methods = %v, want [fido2 passphrase]", r.Methods)
+	}
+}
+
+func TestResolveDevice_DevicePathMatch(t *testing.T) {
+	cfg := &Config{
+		Devices: map[string]DeviceConfig{
+			"sda1": {UUID: "abc-123", Methods: []string{"passphrase"}},
+		},
+	}
+	r := cfg.ResolveDevice("/dev/sda1")
+	if r.UUID != "abc-123" {
+		t.Errorf("UUID = %q, want %q", r.UUID, "abc-123")
+	}
+}
+
+func TestResolveDevice_UnknownReturnsDefaults(t *testing.T) {
+	cfg := &Config{Devices: map[string]DeviceConfig{}}
+	r := cfg.ResolveDevice("nonexistent")
+	if r.UUID != "" {
+		t.Errorf("UUID = %q, want empty", r.UUID)
+	}
+	if len(r.Methods) != 1 || r.Methods[0] != "passphrase" {
+		t.Errorf("Methods = %v, want [passphrase]", r.Methods)
+	}
+}
+
+func TestResolveDevice_EmptyMethodsDefaultsToPassphrase(t *testing.T) {
+	cfg := &Config{
+		Devices: map[string]DeviceConfig{
+			"backup": {UUID: "abc-123"},
+		},
+	}
+	r := cfg.ResolveDevice("backup")
+	if len(r.Methods) != 1 || r.Methods[0] != "passphrase" {
+		t.Errorf("Methods = %v, want [passphrase]", r.Methods)
+	}
+}
+
+func TestAliasFor_Found(t *testing.T) {
+	cfg := &Config{
+		Devices: map[string]DeviceConfig{
+			"backup": {UUID: "abc-123"},
+		},
+	}
+	if alias := cfg.AliasFor("abc-123"); alias != "backup" {
+		t.Errorf("AliasFor = %q, want %q", alias, "backup")
+	}
+}
+
+func TestAliasFor_NotFound(t *testing.T) {
+	cfg := &Config{
+		Devices: map[string]DeviceConfig{
+			"backup": {UUID: "abc-123"},
+		},
+	}
+	if alias := cfg.AliasFor("unknown"); alias != "" {
+		t.Errorf("AliasFor = %q, want empty", alias)
+	}
+}
+
+func TestLoad_MissingFile(t *testing.T) {
+	// Point XDG_CONFIG_HOME to a temp dir with no config.
+	tmp := t.TempDir()
+	t.Setenv("XDG_CONFIG_HOME", tmp)
+
+	cfg := Load()
+	if cfg == nil {
+		t.Fatal("Load returned nil")
+	}
+	if len(cfg.Devices) != 0 {
+		t.Errorf("Devices = %v, want empty", cfg.Devices)
+	}
+}
+
+func TestLoad_ValidYAML(t *testing.T) {
+	tmp := t.TempDir()
+	dir := filepath.Join(tmp, "arca")
+	os.MkdirAll(dir, 0o755)
+	os.WriteFile(filepath.Join(dir, "config.yaml"), []byte(`
+devices:
+  backup:
+    uuid: "abc-123"
+    mountpoint: "/mnt/backup"
+    methods:
+      - fido2
+      - passphrase
+    keyfile: "/path/to/key"
+`), 0o644)
+	t.Setenv("XDG_CONFIG_HOME", tmp)
+
+	cfg := Load()
+	dev, ok := cfg.Devices["backup"]
+	if !ok {
+		t.Fatal("device 'backup' not found in config")
+	}
+	if dev.UUID != "abc-123" {
+		t.Errorf("UUID = %q, want %q", dev.UUID, "abc-123")
+	}
+	if dev.Mountpoint != "/mnt/backup" {
+		t.Errorf("Mountpoint = %q, want %q", dev.Mountpoint, "/mnt/backup")
+	}
+	if len(dev.Methods) != 2 {
+		t.Errorf("Methods = %v, want 2 entries", dev.Methods)
+	}
+	if dev.Keyfile != "/path/to/key" {
+		t.Errorf("Keyfile = %q, want %q", dev.Keyfile, "/path/to/key")
+	}
+}