when(conn.getHeaderField(0)).thenReturn(statusLine);

        // Mock getHeaderFields to return our headers
        Map<String, List<String>> allHeaders = headers != null ? new HashMap<>(headers) : new HashMap<>();
        allHeaders.put(null, Collections.singletonList(statusLine)); // Status line
        when(conn.getHeaderFields()).thenReturn(allHeaders);

        // Mock individual header access by both string key and index

            entry.setValue(Collections.unmodifiableList((List) entry.getValue()));
        }
        return headerFields = Collections.unmodifiableMap(map);
    }

    @Override
    public Map getHeaderFields() {
        if (headerFields != null) {
            return headerFields;
        }
        try {
            handshake();
        } catch (final IOException ex) {}
        return getHeaderFields0();

        }
        return this.headerFields = Collections.unmodifiableMap(map);
    }

    @Override
    public Map<String, List<String>> getHeaderFields() {
        if (this.headerFields != null) {
            return this.headerFields;
        }
        handshake();
        return getHeaderFields0();
    }

    @Override