Add remote storage backend

internal/adapters/storage/fake_test.go

@@ -3,6 +3,9 @@ package storage
 import (
 	"context"
 	"errors"
+	"os"
+	"path/filepath"
+	"strings"
 	"testing"
 )
 
@@ -29,3 +32,84 @@ func TestFakeBackendError(t *testing.T) {
 		t.Fatal("expected error, got nil")
 	}
 }
+
+func TestFakeBackendListPrefixFiltering(t *testing.T) {
+	fake := &FakeBackend{}
+	fake.SeedObject(FakeObject{Key: "dnd/campaigns/forsaken/audio/a.flac", Data: []byte("a")})
+	fake.SeedObject(FakeObject{Key: "dnd/campaigns/forsaken/audio/b.flac", Data: []byte("b")})
+	fake.SeedObject(FakeObject{Key: "dnd/campaigns/other/audio/c.flac", Data: []byte("c")})
+
+	items, err := fake.List(context.Background(), "dnd/campaigns/forsaken/audio/")
+	if err != nil {
+		t.Fatalf("List() error = %v", err)
+	}
+	if len(items) != 2 {
+		t.Fatalf("List() len = %d, want 2", len(items))
+	}
+	if items[0].Key != "dnd/campaigns/forsaken/audio/a.flac" || items[1].Key != "dnd/campaigns/forsaken/audio/b.flac" {
+		t.Fatalf("List() keys = %#v", items)
+	}
+}
+
+func TestFakeBackendDownload(t *testing.T) {
+	fake := &FakeBackend{}
+	fake.SeedObject(FakeObject{Key: "audio/a.flac", Data: []byte("audio-a")})
+
+	dst := filepath.Join(t.TempDir(), "nested", "a.flac")
+	if err := fake.Download(context.Background(), "audio/a.flac", dst); err != nil {
+		t.Fatalf("Download() error = %v", err)
+	}
+	data, err := os.ReadFile(dst)
+	if err != nil {
+		t.Fatalf("ReadFile() error = %v", err)
+	}
+	if string(data) != "audio-a" {
+		t.Fatalf("downloaded content = %q, want %q", string(data), "audio-a")
+	}
+}
+
+func TestFakeBackendUploadAndExists(t *testing.T) {
+	fake := &FakeBackend{}
+
+	local := filepath.Join(t.TempDir(), "upload.txt")
+	if err := os.WriteFile(local, []byte("payload"), 0o644); err != nil {
+		t.Fatalf("WriteFile() error = %v", err)
+	}
+
+	info, err := fake.Upload(context.Background(), local, `runs\id\artifact.txt`, UploadOptions{
+		Metadata: map[string]string{"kind": "artifact"},
+	})
+	if err != nil {
+		t.Fatalf("Upload() error = %v", err)
+	}
+	if info.Key != "runs/id/artifact.txt" {
+		t.Fatalf("Upload() key = %q, want normalized key", info.Key)
+	}
+
+	ok, err := fake.Exists(context.Background(), "runs/id/artifact.txt")
+	if err != nil {
+		t.Fatalf("Exists() error = %v", err)
+	}
+	if !ok {
+		t.Fatal("Exists() = false, want true")
+	}
+}
+
+func TestFakeBackendObjectErrors(t *testing.T) {
+	fake := &FakeBackend{DownloadErr: errors.New("download fail"), UploadErr: errors.New("upload fail"), ListErr: errors.New("list fail"), ExistsErr: errors.New("exists fail")}
+
+	if _, err := fake.List(context.Background(), "x"); err == nil || !strings.Contains(err.Error(), "list fail") {
+		t.Fatalf("List() error = %v, want list fail", err)
+	}
+	if err := fake.Download(context.Background(), "x", filepath.Join(t.TempDir(), "x")); err == nil || !strings.Contains(err.Error(), "download fail") {
+		t.Fatalf("Download() error = %v, want download fail", err)
+	}
+	local := filepath.Join(t.TempDir(), "x.txt")
+	_ = os.WriteFile(local, []byte("x"), 0o644)
+	if _, err := fake.Upload(context.Background(), local, "x", UploadOptions{}); err == nil || !strings.Contains(err.Error(), "upload fail") {
+		t.Fatalf("Upload() error = %v, want upload fail", err)
+	}
+	if _, err := fake.Exists(context.Background(), "x"); err == nil || !strings.Contains(err.Error(), "exists fail") {
+		t.Fatalf("Exists() error = %v, want exists fail", err)
+	}
+}