454 lines
15 KiB
TypeScript
454 lines
15 KiB
TypeScript
/**
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* @license
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* Copyright 2025 Google LLC
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* SPDX-License-Identifier: Apache-2.0
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*/
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import assert from 'node:assert';
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import {rm, stat, mkdir, chmod, writeFile} from 'node:fs/promises';
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import {tmpdir} from 'node:os';
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import {join} from 'node:path';
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import {describe, it} from 'node:test';
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import type {ParsedArguments} from '../../src/bin/chrome-devtools-mcp-cli-options.js';
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import {TextSnapshot} from '../../src/TextSnapshot.js';
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import {screenshot} from '../../src/tools/screenshot.js';
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import {screenshots} from '../snapshot.js';
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import {html, withMcpContext} from '../utils.js';
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const screenshotTool = screenshot({} as ParsedArguments);
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/**
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* Reads the pixel width from a PNG buffer's IHDR chunk (bytes 16..19).
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*/
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function pngWidth(data: Buffer): number {
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return data.readUInt32BE(16);
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}
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/**
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* Reads the pixel height from a PNG buffer's IHDR chunk (bytes 20..23).
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*/
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function pngHeight(data: Buffer): number {
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return data.readUInt32BE(20);
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}
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describe('screenshot', () => {
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describe('browser_take_screenshot', () => {
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it('with default options', async () => {
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await withMcpContext(async (response, context) => {
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const fixture = screenshots.basic;
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const page = context.getSelectedMcpPage().pptrPage;
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await page.setContent(fixture.html);
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await screenshotTool.handler(
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{params: {format: 'png'}, page: context.getSelectedMcpPage()},
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response,
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context,
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);
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assert.equal(response.images.length, 1);
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assert.equal(response.images[0].mimeType, 'image/png');
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assert.equal(
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response.responseLines.at(0),
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"Took a screenshot of the current page's viewport.",
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);
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});
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});
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it('ignores quality', async () => {
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await withMcpContext(async (response, context) => {
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const fixture = screenshots.basic;
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const page = context.getSelectedMcpPage().pptrPage;
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await page.setContent(fixture.html);
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await screenshotTool.handler(
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{
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params: {format: 'png', quality: 0},
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page: context.getSelectedMcpPage(),
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},
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response,
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context,
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);
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assert.equal(response.images.length, 1);
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assert.equal(response.images[0].mimeType, 'image/png');
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assert.equal(
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response.responseLines.at(0),
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"Took a screenshot of the current page's viewport.",
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);
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});
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});
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it('with jpeg', async () => {
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await withMcpContext(async (response, context) => {
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await screenshotTool.handler(
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{params: {format: 'jpeg'}, page: context.getSelectedMcpPage()},
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response,
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context,
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);
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assert.equal(response.images.length, 1);
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assert.equal(response.images[0].mimeType, 'image/jpeg');
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assert.equal(
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response.responseLines.at(0),
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"Took a screenshot of the current page's viewport.",
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);
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});
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});
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it('with webp', async () => {
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await withMcpContext(async (response, context) => {
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await screenshotTool.handler(
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{params: {format: 'webp'}, page: context.getSelectedMcpPage()},
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response,
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context,
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);
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assert.equal(response.images.length, 1);
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assert.equal(response.images[0].mimeType, 'image/webp');
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assert.equal(
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response.responseLines.at(0),
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"Took a screenshot of the current page's viewport.",
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);
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});
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});
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it('with full page', async () => {
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await withMcpContext(async (response, context) => {
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const fixture = screenshots.viewportOverflow;
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const page = context.getSelectedMcpPage().pptrPage;
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await page.setContent(fixture.html);
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await screenshotTool.handler(
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{
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params: {format: 'png', fullPage: true},
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page: context.getSelectedMcpPage(),
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},
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response,
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context,
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);
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assert.equal(response.images.length, 1);
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assert.equal(response.images[0].mimeType, 'image/png');
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assert.equal(
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response.responseLines.at(0),
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'Took a screenshot of the full current page.',
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);
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});
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});
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it('with full page resulting in a large screenshot', async () => {
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await withMcpContext(async (response, context) => {
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const page = context.getSelectedMcpPage().pptrPage;
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await page.setContent(
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html`${`<div style="color:blue;">test</div>`.repeat(6500)}
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<div
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id="red"
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style="color:blue;"
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>test</div
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> `,
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);
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await page.evaluate(() => {
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const el = document.querySelector('#red');
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return el?.scrollIntoViewIfNeeded();
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});
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await screenshotTool.handler(
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{
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params: {format: 'png', fullPage: true},
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page: context.getSelectedMcpPage(),
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},
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response,
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context,
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);
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assert.equal(response.images.length, 0);
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assert.equal(
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response.responseLines.at(0),
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'Took a screenshot of the full current page.',
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);
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assert.ok(
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response.responseLines.at(1)?.match(/Saved screenshot to.*\.png/),
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);
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});
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});
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it('with element uid', async () => {
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await withMcpContext(async (response, context) => {
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const fixture = screenshots.button;
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const page = context.getSelectedMcpPage().pptrPage;
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await page.setContent(fixture.html);
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context.getSelectedMcpPage().textSnapshot = await TextSnapshot.create(
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context.getSelectedMcpPage(),
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);
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await screenshotTool.handler(
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{
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params: {
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format: 'png',
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uid: '1_1',
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},
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page: context.getSelectedMcpPage(),
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},
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response,
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context,
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);
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assert.equal(response.images.length, 1);
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assert.equal(response.images[0].mimeType, 'image/png');
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assert.equal(
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response.responseLines.at(0),
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'Took a screenshot of node with uid "1_1".',
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);
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});
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});
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it('with filePath', async () => {
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await withMcpContext(async (response, context) => {
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const filePath = join(tmpdir(), 'test-screenshot.png');
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try {
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const fixture = screenshots.basic;
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const page = context.getSelectedMcpPage().pptrPage;
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await page.setContent(fixture.html);
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await screenshotTool.handler(
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{
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params: {format: 'png', filePath},
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page: context.getSelectedMcpPage(),
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},
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response,
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context,
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);
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assert.equal(response.images.length, 0);
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assert.equal(
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response.responseLines.at(0),
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"Took a screenshot of the current page's viewport.",
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);
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assert.equal(
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response.responseLines.at(1),
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`Saved screenshot to ${filePath}.`,
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);
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const stats = await stat(filePath);
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assert.ok(stats.isFile());
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assert.ok(stats.size > 0);
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} finally {
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await rm(filePath, {force: true});
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}
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});
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});
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it('with unwritable filePath', async () => {
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if (process.platform === 'win32') {
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const filePath = join(
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tmpdir(),
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'readonly-file-for-screenshot-test.png',
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);
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// Create the file and make it read-only.
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await writeFile(filePath, '');
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await chmod(filePath, 0o400);
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try {
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await withMcpContext(async (response, context) => {
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const fixture = screenshots.basic;
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const page = context.getSelectedMcpPage().pptrPage;
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await page.setContent(fixture.html);
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await assert.rejects(
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screenshotTool.handler(
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{
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params: {format: 'png', filePath},
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page: context.getSelectedMcpPage(),
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},
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response,
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context,
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),
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);
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});
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} finally {
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// Make the file writable again so it can be deleted.
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await chmod(filePath, 0o600);
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await rm(filePath, {force: true});
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}
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} else {
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const dir = join(tmpdir(), 'readonly-dir-for-screenshot-test');
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await mkdir(dir, {recursive: true});
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await chmod(dir, 0o500);
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const filePath = join(dir, 'test-screenshot.png');
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try {
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await withMcpContext(async (response, context) => {
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const fixture = screenshots.basic;
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const page = context.getSelectedMcpPage().pptrPage;
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await page.setContent(fixture.html);
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await assert.rejects(
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screenshotTool.handler(
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{
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params: {format: 'png', filePath},
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page: context.getSelectedMcpPage(),
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},
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response,
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context,
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),
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);
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});
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} finally {
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await chmod(dir, 0o700);
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await rm(dir, {recursive: true, force: true});
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}
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}
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});
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it('honors screenshotFormat default from CLI args', async () => {
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const tool = screenshot({
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screenshotFormat: 'jpeg',
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} as ParsedArguments);
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await withMcpContext(async (response, context) => {
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const fixture = screenshots.basic;
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const page = context.getSelectedMcpPage().pptrPage;
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await page.setContent(fixture.html);
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// No explicit format passed: zod should apply the CLI-driven default.
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await tool.handler(
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{
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params: {format: tool.schema.format.parse(undefined)},
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page: context.getSelectedMcpPage(),
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},
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response,
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context,
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);
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assert.equal(response.images.length, 1);
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assert.equal(response.images[0].mimeType, 'image/jpeg');
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});
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});
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it('keeps "png" as default format when no CLI override is set', async () => {
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const tool = screenshot({} as ParsedArguments);
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assert.equal(tool.schema.format.parse(undefined), 'png');
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});
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it('downscales viewport screenshot when screenshotMaxWidth is set', async () => {
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const tool = screenshot({
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screenshotMaxWidth: 100,
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} as ParsedArguments);
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await withMcpContext(async (response, context) => {
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const page = context.getSelectedMcpPage().pptrPage;
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await page.setViewport({width: 800, height: 600});
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await page.setContent(
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html`<div style="width:100vw;height:100vh;background:red"></div>`,
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);
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await tool.handler(
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{params: {format: 'png'}, page: context.getSelectedMcpPage()},
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response,
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context,
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);
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assert.equal(response.images.length, 1);
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const buf = Buffer.from(response.images[0].data, 'base64');
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assert.equal(pngWidth(buf), 100);
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// Aspect ratio preserved: 800x600 -> 100x75.
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assert.equal(pngHeight(buf), 75);
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});
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});
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it('downscales using the smaller scale when both max-width and max-height are set', async () => {
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const tool = screenshot({
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screenshotMaxWidth: 400,
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screenshotMaxHeight: 60,
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} as ParsedArguments);
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await withMcpContext(async (response, context) => {
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const page = context.getSelectedMcpPage().pptrPage;
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await page.setViewport({width: 800, height: 600});
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await page.setContent(
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html`<div style="width:100vw;height:100vh"></div>`,
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);
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await tool.handler(
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{params: {format: 'png'}, page: context.getSelectedMcpPage()},
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response,
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context,
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);
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const buf = Buffer.from(response.images[0].data, 'base64');
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// height bound dictates: 60/600 = 0.1 -> 80x60.
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assert.equal(pngHeight(buf), 60);
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assert.equal(pngWidth(buf), 80);
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});
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});
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it('does not resize when source is smaller than the max bounds', async () => {
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const tool = screenshot({
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screenshotMaxWidth: 4000,
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screenshotMaxHeight: 4000,
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} as ParsedArguments);
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await withMcpContext(async (response, context) => {
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const page = context.getSelectedMcpPage().pptrPage;
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await page.setViewport({width: 800, height: 600});
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await page.setContent(html`<div></div>`);
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await tool.handler(
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{params: {format: 'png'}, page: context.getSelectedMcpPage()},
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response,
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context,
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);
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const buf = Buffer.from(response.images[0].data, 'base64');
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assert.equal(pngWidth(buf), 800);
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assert.equal(pngHeight(buf), 600);
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});
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});
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it('downscales full page screenshot when screenshotMaxWidth is set', async () => {
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const tool = screenshot({
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screenshotMaxWidth: 200,
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} as ParsedArguments);
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await withMcpContext(async (response, context) => {
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const page = context.getSelectedMcpPage().pptrPage;
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await page.setViewport({width: 800, height: 600});
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await page.setContent(
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html`<style>
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body {
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margin: 0;
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}</style
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><div style="width:1000px;height:1500px;background:red"></div>`,
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);
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await tool.handler(
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{
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params: {format: 'png', fullPage: true},
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page: context.getSelectedMcpPage(),
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},
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response,
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context,
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);
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const buf = Buffer.from(response.images[0].data, 'base64');
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// Source is at least 1000x1500; scale = 200/1000 = 0.2 -> ~200x300.
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// Allow ±2px to absorb sub-pixel rasterization rounding by Chrome.
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assert.equal(pngWidth(buf), 200);
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assert.ok(
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Math.abs(pngHeight(buf) - 300) <= 2,
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`expected height near 300, got ${pngHeight(buf)}`,
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);
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});
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});
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it('with malformed filePath', async () => {
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await withMcpContext(async (response, context) => {
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// Use a platform-specific invalid character.
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// On Windows, characters like '<', '>', ':', '"', '/', '\', '|', '?', '*' are invalid.
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// On POSIX, the null byte is invalid.
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const invalidChar = process.platform === 'win32' ? '>' : '\0';
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const filePath = `malformed${invalidChar}path.png`;
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const fixture = screenshots.basic;
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const page = context.getSelectedMcpPage().pptrPage;
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await page.setContent(fixture.html);
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await assert.rejects(
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screenshotTool.handler(
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{
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params: {format: 'png', filePath},
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page: context.getSelectedMcpPage(),
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},
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response,
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context,
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),
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);
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});
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});
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});
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});
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