test: lock down multi-root storage isolation

chfs-ng/internal/storage/multipath_test.go

@@ -6,36 +6,43 @@ import (
 	"testing"
 )
 
-func TestNewMultiKeepsDuplicateBasenames(t *testing.T) {
-	root := t.TempDir()
-	first := filepath.Join(root, "same")
-	second := filepath.Join(root, "other", "same")
-	if err := os.MkdirAll(first, 0o755); err != nil {
-		t.Fatal(err)
+func TestMultiUsesUniqueVirtualRootNames(t *testing.T) {
+	a := t.TempDir()
+	b := t.TempDir()
+	m := NewMulti([]string{a, b})
+	if len(m.Names) != 2 || m.Names[0] == m.Names[1] {
+		t.Fatalf("names=%v", m.Names)
 	}
-	if err := os.MkdirAll(second, 0o755); err != nil {
-		t.Fatal(err)
+	if _, _, ok := m.FindRoot(m.Names[0]); !ok {
+		t.Fatal("first root not addressable")
 	}
-	m := NewMulti([]string{first, second})
-	if len(m.Roots) != 2 || len(m.Names) != 2 {
-		t.Fatalf("duplicate basename dropped: roots=%d names=%v", len(m.Roots), m.Names)
-	}
-	if m.Names[0] != "same" || m.Names[1] != "same-2" {
-		t.Fatalf("unexpected virtual names: %v", m.Names)
+	if _, _, ok := m.FindRoot(m.Names[1]); !ok {
+		t.Fatal("second root not addressable")
 	}
 }
 
-func TestMultiRejectsMutationOfVirtualRoot(t *testing.T) {
-	root1 := t.TempDir()
-	root2 := t.TempDir()
-	m := NewMulti([]string{root1, root2})
-	if err := m.Remove(m.Names[0]); err == nil {
-		t.Fatal("expected virtual root removal to be rejected")
+func TestMultiRenameCannotCrossRoots(t *testing.T) {
+	a := t.TempDir()
+	b := t.TempDir()
+	if err := os.WriteFile(filepath.Join(a, "src.txt"), []byte("src"), 0o644); err != nil {
+		t.Fatal(err)
 	}
-	if _, err := m.Create(m.Names[0]); err == nil {
-		t.Fatal("expected virtual root creation to be rejected")
+	m := NewMulti([]string{a, b})
+	err := m.Rename(m.Names[0]+"/src.txt", m.Names[1]+"/dst.txt")
+	if err == nil {
+		t.Fatal("expected cross-root rename to fail")
 	}
-	if err := m.Rename(m.Names[0], m.Names[1]); err == nil {
-		t.Fatal("expected virtual root rename to be rejected")
+	if _, err := os.Stat(filepath.Join(a, "src.txt")); err != nil {
+		t.Fatalf("source disappeared: %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(b, "dst.txt")); !os.IsNotExist(err) {
+		t.Fatalf("destination unexpectedly created: %v", err)
+	}
+}
+
+func TestMultiRemoveCannotRemoveVirtualRoot(t *testing.T) {
+	m := NewMulti([]string{t.TempDir()})
+	if err := m.Remove(""); err == nil {
+		t.Fatal("expected virtual root removal to fail")
 	}
 }