test(parsing): add 229 unit tests across 18 config/parsing packages

Covering nil-input safety, plugin backends (HTTP/gRPC/default), loaders
(File/HTTP/Redis), selector strategies, edge cases (empty/invalid inputs),
and hop-to-node metadata inheritance. All tests passing.

config/parsing/chain/parse_test.go

@@ -0,0 +1,121 @@
+package chain
+
+import (
+	"io"
+	"testing"
+
+	"github.com/go-gost/core/logger"
+	"github.com/go-gost/x/config"
+	xlogger "github.com/go-gost/x/logger"
+)
+
+func TestMain(m *testing.M) {
+	logger.SetDefault(xlogger.NewLogger(xlogger.OutputOption(io.Discard)))
+	m.Run()
+}
+
+func testLogger() logger.Logger {
+	return xlogger.NewLogger(xlogger.OutputOption(io.Discard))
+}
+
+func TestParseChain_Nil(t *testing.T) {
+	c, err := ParseChain(nil, testLogger())
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if c != nil {
+		t.Fatal("expected nil for nil config")
+	}
+}
+
+func TestParseChain_EmptyHops(t *testing.T) {
+	c, err := ParseChain(&config.ChainConfig{
+		Name: "empty-hops",
+		Hops: []*config.HopConfig{},
+	}, testLogger())
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if c == nil {
+		t.Fatal("expected non-nil chain")
+	}
+}
+
+func TestParseChain_NilHops(t *testing.T) {
+	c, err := ParseChain(&config.ChainConfig{
+		Name: "nil-hops",
+		Hops: nil,
+	}, testLogger())
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if c == nil {
+		t.Fatal("expected non-nil chain")
+	}
+}
+
+func TestParseChain_NilHopEntry(t *testing.T) {
+	c, err := ParseChain(&config.ChainConfig{
+		Name: "nil-entry",
+		Hops: []*config.HopConfig{nil},
+	}, testLogger())
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if c == nil {
+		t.Fatal("expected non-nil chain when hop entry is nil")
+	}
+}
+
+func TestParseChain_WithMetadata(t *testing.T) {
+	c, err := ParseChain(&config.ChainConfig{
+		Name: "meta-chain",
+		Metadata: map[string]any{
+			"key": "value",
+		},
+	}, testLogger())
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if c == nil {
+		t.Fatal("expected non-nil chain")
+	}
+}
+
+func TestParseChain_NamedHop(t *testing.T) {
+	// Named hop (Nodes==nil, Plugin==nil) uses registry lookup
+	c, err := ParseChain(&config.ChainConfig{
+		Name: "named-hop",
+		Hops: []*config.HopConfig{
+			{Name: "nonexistent-hop"},
+		},
+	}, testLogger())
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if c == nil {
+		t.Fatal("expected non-nil chain even with unregistered hop")
+	}
+}
+
+func TestParseChain_InlineHopWithPlugin(t *testing.T) {
+	// Inline hop (Nodes!=nil or Plugin!=nil) calls hop_parser.ParseHop
+	c, err := ParseChain(&config.ChainConfig{
+		Name: "inline-hop",
+		Hops: []*config.HopConfig{
+			{
+				Name: "plugin-hop",
+				Plugin: &config.PluginConfig{
+					Type: "http",
+					Addr: "127.0.0.1:9000",
+				},
+			},
+		},
+	}, testLogger())
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if c == nil {
+		t.Fatal("expected non-nil chain")
+	}
+}