Add unit test for storeFailedAdvisory

cmd/csaf_downloader/forwarder.go

@@ -187,16 +187,10 @@ func (f *forwarder) buildRequest(
 // storeFailedAdvisory stores an advisory in a special folder
 // in case the forwarding failed.
 func (f *forwarder) storeFailedAdvisory(filename, doc, sha256, sha512 string) error {
-	dir := filepath.Join(f.cfg.Directory, failedForwardDir)
 	// Create special folder if it does not exist.
-	if _, err := os.Stat(dir); err != nil {
-		if os.IsNotExist(err) {
-			if err := os.MkdirAll(dir, 0755); err != nil {
-				return err
-			}
-		} else {
-			return err
-		}
+	dir := filepath.Join(f.cfg.Directory, failedForwardDir)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return err
 	}
 	// Store parts which are not empty.
 	for _, x := range []struct {

cmd/csaf_downloader/forwarder_test.go

@@ -18,6 +18,7 @@ import (
 	"mime/multipart"
 	"net/http"
 	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 
@@ -237,3 +238,46 @@ func TestLimitedString(t *testing.T) {
 		t.Fatal("expected to fail with an error")
 	}
 }
+
+func TestStoreFailedAdvisory(t *testing.T) {
+	dir, err := os.MkdirTemp("", "storeFailed")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		os.Chmod(dir, 0700)
+		os.RemoveAll(dir)
+	}()
+
+	cfg := &config{Directory: dir}
+	fw := newForwarder(cfg)
+
+	badDir := filepath.Join(dir, failedForwardDir)
+	if err := os.WriteFile(badDir, []byte("test"), 0664); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := fw.storeFailedAdvisory("advisory.json", "{}", "256", "512"); err == nil {
+		t.Fatal("if the destination exists as a file an error should occur")
+	}
+
+	if err := os.Remove(badDir); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := fw.storeFailedAdvisory("advisory.json", "{}", "256", "512"); err != nil {
+		t.Fatal(err)
+	}
+
+	sha256Path := filepath.Join(dir, failedForwardDir, "advisory.json.sha256")
+
+	// Write protect advisory.
+	if err := os.Chmod(sha256Path, 0); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := fw.storeFailedAdvisory("advisory.json", "{}", "256", "512"); err == nil {
+		t.Fatal("expected to fail with an error")
+	}
+
+}