Finish output directory follow-up work

internal/app/output_test.go

@@ -0,0 +1,38 @@
+package app
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestResolveOutputDirRejectsDanglingSymlinkComponents(t *testing.T) {
+	workingDir := t.TempDir()
+	dangling := filepath.Join(workingDir, "dangling")
+	if err := os.Symlink(filepath.Join(workingDir, "missing"), dangling); err != nil {
+		t.Fatal(err)
+	}
+
+	for _, directory := range []string{dangling, filepath.Join(dangling, "reports")} {
+		t.Run(filepath.Base(directory), func(t *testing.T) {
+			if _, err := resolveOutputDir(workingDir, directory); err == nil {
+				t.Fatalf("resolveOutputDir(%q) error = nil, want dangling symlink error", directory)
+			}
+		})
+	}
+}
+
+func TestResolveOutputDirAllowsMissingDirectoryBelowValidSymlink(t *testing.T) {
+	workingDir := t.TempDir()
+	target := t.TempDir()
+	link := filepath.Join(workingDir, "linked")
+	if err := os.Symlink(target, link); err != nil {
+		t.Fatal(err)
+	}
+
+	directory := filepath.Join(link, "reports")
+	got, err := resolveOutputDir(workingDir, directory)
+	if err != nil || got != directory {
+		t.Fatalf("resolveOutputDir() = %q, %v, want %q, nil", got, err, directory)
+	}
+}