if _, err := f.WriteString(tc.initialFileContents); err != nil {
				t.Fatalf("Failed to write to file: %v", err)
			}
			f.Close()
			args := fmt.Sprintf("source configure-helper.sh; append_or_replace_prefixed_line %s %s %s", f.Name(), tc.prefix, tc.suffix)
			cmd := exec.Command("bash", "-c", args)
			stderr, err := cmd.CombinedOutput()
			if err != nil {
				t.Fatalf("Failed to run command: %v: %s", err, stderr)
			}