diff --git a/test/browsercontext-cookies.spec.ts b/test/browsercontext-cookies.spec.ts
index 5daf4f49b0..6a9af49348 100644
--- a/test/browsercontext-cookies.spec.ts
+++ b/test/browsercontext-cookies.spec.ts
@@ -74,7 +74,7 @@ it('should properly report httpOnly cookie', async ({context, page, server}) =>
 });
 
 it('should properly report "Strict" sameSite cookie', (test, parameters) => {
-  test.fail(options.WEBKIT(parameters) && WIN);
+  test.fail(options.WEBKIT(parameters) && options.WIN(parameters));
 }, async ({context, page, server}) => {
   server.setRoute('/empty.html', (req, res) => {
     res.setHeader('Set-Cookie', 'name=value;SameSite=Strict');
@@ -87,7 +87,7 @@ it('should properly report "Strict" sameSite cookie', (test, parameters) => {
 });
 
 it('should properly report "Lax" sameSite cookie', (test, parameters) => {
-  test.fail(options.WEBKIT(parameters) && WIN);
+  test.fail(options.WEBKIT(parameters) && options.WIN(parameters));
 }, async ({context, page, server}) => {
   server.setRoute('/empty.html', (req, res) => {
     res.setHeader('Set-Cookie', 'name=value;SameSite=Lax');
diff --git a/test/browsercontext-page-event.spec.ts b/test/browsercontext-page-event.spec.ts
index edf4fd13e6..0ba24c8a72 100644
--- a/test/browsercontext-page-event.spec.ts
+++ b/test/browsercontext-page-event.spec.ts
@@ -175,14 +175,14 @@ it('should work with Shift-clicking', (test, parameters) => {
 it('should work with Ctrl-clicking', (test, parameters) => {
   test.fixme(options.WEBKIT(parameters), 'Ctrl+Click does not open a new tab.');
   test.fixme(options.FIREFOX(parameters), 'Reports an opener in this case.');
-}, async ({browser, server}) => {
+}, async ({browser, server, isMac}) => {
   const context = await browser.newContext();
   const page = await context.newPage();
   await page.goto(server.EMPTY_PAGE);
   await page.setContent('<a href="/one-style.html">yo</a>');
   const [popup] = await Promise.all([
     context.waitForEvent('page'),
-    page.click('a', { modifiers: [ MAC ? 'Meta' : 'Control'] }),
+    page.click('a', { modifiers: [ isMac ? 'Meta' : 'Control'] }),
   ]);
   expect(await popup.opener()).toBe(null);
   await context.close();
diff --git a/test/capabilities.spec.ts b/test/capabilities.spec.ts
index c97d1e70af..1271ef5850 100644
--- a/test/capabilities.spec.ts
+++ b/test/capabilities.spec.ts
@@ -18,7 +18,7 @@ import url from 'url';
 import { it, expect, options } from './playwright.fixtures';
 
 it('Web Assembly should work', (test, parameters) => {
-  test.fail(options.WEBKIT(parameters) && WIN);
+  test.fail(options.WEBKIT(parameters) && options.WIN(parameters));
 }, async function({page, server}) {
   await page.goto(server.PREFIX + '/wasm/table2.html');
   expect(await page.evaluate('loadTable()')).toBe('42, 83');
@@ -51,7 +51,7 @@ it('should respect CSP', async ({page, server}) => {
 });
 
 it('should play video', (test, parameters) => {
-  test.fixme(options.WEBKIT(parameters) && (WIN || LINUX));
+  test.fixme(options.WEBKIT(parameters) && (options.WIN(parameters) || options.LINUX(parameters)));
 }, async ({page, asset, isWebKit}) => {
   // TODO: the test passes on Windows locally but fails on GitHub Action bot,
   // apparently due to a Media Pack issue in the Windows Server.
diff --git a/test/chromium/launcher.spec.ts b/test/chromium/launcher.spec.ts
index b8c9455a78..1e55925c34 100644
--- a/test/chromium/launcher.spec.ts
+++ b/test/chromium/launcher.spec.ts
@@ -39,7 +39,7 @@ it('should not throw with remote-debugging-port argument', (test, parameters) =>
 });
 
 it('should open devtools when "devtools: true" option is given', (test, parameters) => {
-  test.skip(!options.CHROMIUM(parameters) || options.WIRE || WIN);
+  test.skip(!options.CHROMIUM(parameters) || options.WIRE || options.WIN(parameters));
 }, async ({browserType, defaultBrowserOptions}) => {
   let devtoolsCallback;
   const devtoolsPromise = new Promise(f => devtoolsCallback = f);
diff --git a/test/defaultbrowsercontext-2.spec.ts b/test/defaultbrowsercontext-2.spec.ts
index 6c0cfa0408..8005e1fe37 100644
--- a/test/defaultbrowsercontext-2.spec.ts
+++ b/test/defaultbrowsercontext-2.spec.ts
@@ -69,7 +69,7 @@ it('should support ignoreHTTPSErrors option', async ({httpsServer, launchPersist
 });
 
 it('should support extraHTTPHeaders option', (test, parameters) => {
-  test.flaky(options.FIREFOX(parameters) && !options.HEADLESS && LINUX, 'Intermittent timeout on bots');
+  test.flaky(options.FIREFOX(parameters) && !options.HEADLESS && options.LINUX(parameters), 'Intermittent timeout on bots');
 }, async ({server, launchPersistent}) => {
   const {page} = await launchPersistent({extraHTTPHeaders: { foo: 'bar' }});
   const [request] = await Promise.all([
diff --git a/test/dialog.spec.ts b/test/dialog.spec.ts
index c773cf1fec..7e064e8477 100644
--- a/test/dialog.spec.ts
+++ b/test/dialog.spec.ts
@@ -63,7 +63,7 @@ it('should dismiss the confirm prompt', async ({page}) => {
 });
 
 it('should be able to close context with open alert', (test, parameters) => {
-  test.fixme(options.WEBKIT(parameters) && MAC);
+  test.fixme(options.WEBKIT(parameters) && options.MAC(parameters));
 }, async ({browser}) => {
   const context = await browser.newContext();
   const page = await context.newPage();
diff --git a/test/elementhandle-owner-frame.spec.ts b/test/elementhandle-owner-frame.spec.ts
index d7389a2210..f07f3ffd05 100644
--- a/test/elementhandle-owner-frame.spec.ts
+++ b/test/elementhandle-owner-frame.spec.ts
@@ -35,7 +35,7 @@ it('should work for cross-process iframes', async ({ page, server }) => {
 });
 
 it('should work for document', (test, parameters) => {
-  test.flaky(WIN && options.WEBKIT(parameters));
+  test.flaky(options.WIN(parameters) && options.WEBKIT(parameters));
 }, async ({ page, server }) => {
   await page.goto(server.EMPTY_PAGE);
   await utils.attachFrame(page, 'frame1', server.EMPTY_PAGE);
diff --git a/test/elementhandle-screenshot.spec.ts b/test/elementhandle-screenshot.spec.ts
index 2c44bc2b22..f29324c22a 100644
--- a/test/elementhandle-screenshot.spec.ts
+++ b/test/elementhandle-screenshot.spec.ts
@@ -363,7 +363,7 @@ describe('element screenshot', (suite, parameters) => {
   });
 
   it('should wait for element to stop moving', (test, parameters) => {
-    test.flaky(options.WEBKIT(parameters) && !options.HEADLESS && LINUX);
+    test.flaky(options.WEBKIT(parameters) && !options.HEADLESS && options.LINUX(parameters));
   }, async ({ page, server, golden }) => {
     await page.setViewportSize({ width: 500, height: 500 });
     await page.goto(server.PREFIX + '/grid.html');
diff --git a/test/elementhandle-wait-for-element-state.spec.ts b/test/elementhandle-wait-for-element-state.spec.ts
index 1011fdb1ee..d7259e6201 100644
--- a/test/elementhandle-wait-for-element-state.spec.ts
+++ b/test/elementhandle-wait-for-element-state.spec.ts
@@ -115,7 +115,7 @@ it('should wait for disabled button', async ({page}) => {
 });
 
 it('should wait for stable position', (test, parameters) => {
-  test.fixme(options.FIREFOX(parameters) && LINUX);
+  test.fixme(options.FIREFOX(parameters) && options.LINUX(parameters));
 }, async ({page, server}) => {
   await page.goto(server.PREFIX + '/input/button.html');
   const button = await page.$('button');
diff --git a/test/fixtures.spec.ts b/test/fixtures.spec.ts
index 745a355825..b61f27e294 100644
--- a/test/fixtures.spec.ts
+++ b/test/fixtures.spec.ts
@@ -45,20 +45,20 @@ defineTestFixture('stallingConnectedRemoteServer', async ({browserType, stalling
   await browser.close();
 });
 
-it('should close the browser when the node process closes', (test, parameters) => {
+it('should close the browser when the node process closes', test => {
   test.slow();
-}, async ({connectedRemoteServer}) => {
-  if (WIN)
+}, async ({connectedRemoteServer, isWindows}) => {
+  if (isWindows)
     execSync(`taskkill /pid ${connectedRemoteServer.child().pid} /T /F`);
   else
     process.kill(connectedRemoteServer.child().pid);
-  expect(await connectedRemoteServer.childExitCode()).toBe(WIN ? 1 : 0);
+  expect(await connectedRemoteServer.childExitCode()).toBe(isWindows ? 1 : 0);
   // We might not get browser exitCode in time when killing the parent node process,
   // so we don't check it here.
 });
 
-describe('fixtures', suite => {
-  suite.skip(WIN || !options.HEADLESS);
+describe('fixtures', (suite, parameters) => {
+  suite.skip(options.WIN(parameters) || !options.HEADLESS);
   suite.slow();
 }, () => {
   // Cannot reliably send signals on Windows.
diff --git a/test/focus.spec.ts b/test/focus.spec.ts
index 8fc24f1998..5d8a232c58 100644
--- a/test/focus.spec.ts
+++ b/test/focus.spec.ts
@@ -79,7 +79,7 @@ it('should traverse focus in all directions', async function({page}) {
 });
 
 it('should traverse only form elements', (test, parameters) => {
-  test.skip(!MAC || !options.WEBKIT(parameters),
+  test.skip(!options.MAC(parameters) || !options.WEBKIT(parameters),
       'Chromium and WebKit both have settings for tab traversing all links, but it is only on by default in WebKit.');
 }, async function({page}) {
   await page.setContent(`
diff --git a/test/headful.spec.ts b/test/headful.spec.ts
index 89355bdf0a..0180f28c13 100644
--- a/test/headful.spec.ts
+++ b/test/headful.spec.ts
@@ -27,7 +27,7 @@ it('should have default url when launching browser', async ({browserType, defaul
 });
 
 it('headless should be able to read cookies written by headful', (test, parameters) => {
-  test.fail(WIN && options.CHROMIUM(parameters));
+  test.fail(options.WIN(parameters) && options.CHROMIUM(parameters));
   test.flaky(options.FIREFOX(parameters));
   test.slow();
 }, async ({browserType, defaultBrowserOptions, server}) => {
diff --git a/test/keyboard.spec.ts b/test/keyboard.spec.ts
index 25cfc2df78..cd537fa099 100644
--- a/test/keyboard.spec.ts
+++ b/test/keyboard.spec.ts
@@ -84,7 +84,7 @@ it('insertText should only emit input event', async ({page, server}) => {
 });
 
 it('should report shiftKey', (test, parameters) => {
-  test.fail(options.FIREFOX(parameters) && MAC);
+  test.fail(options.FIREFOX(parameters) && options.MAC(parameters));
 }, async ({page, server}) => {
   await page.goto(server.PREFIX + '/input/keyboard.html');
   const keyboard = page.keyboard;
@@ -312,11 +312,11 @@ it('should type emoji into an iframe', async ({page, server}) => {
   expect(await frame.$eval('textarea', textarea => textarea.value)).toBe('👹 Tokyo street Japan 🇯🇵');
 });
 
-it('should handle selectAll', async ({page, server}) => {
+it('should handle selectAll', async ({page, server, isMac}) => {
   await page.goto(server.PREFIX + '/input/textarea.html');
   const textarea = await page.$('textarea');
   await textarea.type('some text');
-  const modifier = MAC ? 'Meta' : 'Control';
+  const modifier = isMac ? 'Meta' : 'Control';
   await page.keyboard.down(modifier);
   await page.keyboard.press('a');
   await page.keyboard.up(modifier);
@@ -324,7 +324,7 @@ it('should handle selectAll', async ({page, server}) => {
   expect(await page.$eval('textarea', textarea => textarea.value)).toBe('');
 });
 
-it('should be able to prevent selectAll', async ({page, server}) => {
+it('should be able to prevent selectAll', async ({page, server, isMac}) => {
   await page.goto(server.PREFIX + '/input/textarea.html');
   const textarea = await page.$('textarea');
   await textarea.type('some text');
@@ -334,7 +334,7 @@ it('should be able to prevent selectAll', async ({page, server}) => {
         event.preventDefault();
     }, false);
   });
-  const modifier = MAC ? 'Meta' : 'Control';
+  const modifier = isMac ? 'Meta' : 'Control';
   await page.keyboard.down(modifier);
   await page.keyboard.press('a');
   await page.keyboard.up(modifier);
@@ -343,7 +343,7 @@ it('should be able to prevent selectAll', async ({page, server}) => {
 });
 
 it('should support MacOS shortcuts', (test, parameters) => {
-  test.skip(!MAC);
+  test.skip(!options.MAC(parameters));
 }, async ({page, server}) => {
   await page.goto(server.PREFIX + '/input/textarea.html');
   const textarea = await page.$('textarea');
@@ -354,11 +354,11 @@ it('should support MacOS shortcuts', (test, parameters) => {
   expect(await page.$eval('textarea', textarea => textarea.value)).toBe('some ');
 });
 
-it('should press the meta key', async ({page, isFirefox}) => {
+it('should press the meta key', async ({page, isFirefox, isMac}) => {
   const lastEvent = await captureLastKeydown(page);
   await page.keyboard.press('Meta');
   const {key, code, metaKey} = await lastEvent.jsonValue();
-  if (isFirefox && !MAC)
+  if (isFirefox && !isMac)
     expect(key).toBe('OS');
   else
     expect(key).toBe('Meta');
@@ -368,7 +368,7 @@ it('should press the meta key', async ({page, isFirefox}) => {
   else
     expect(code).toBe('MetaLeft');
 
-  if (isFirefox && !MAC)
+  if (isFirefox && !isMac)
     expect(metaKey).toBe(false);
   else
     expect(metaKey).toBe(true);
diff --git a/test/mouse.spec.ts b/test/mouse.spec.ts
index 1af09d3b75..a221f58b41 100644
--- a/test/mouse.spec.ts
+++ b/test/mouse.spec.ts
@@ -28,7 +28,7 @@ function dimensions() {
 }
 
 it('should click the document', (test, parameters) => {
-  test.flaky(options.FIREFOX(parameters) && WIN, 'Occasionally times out on options.FIREFOX on Windows: https://github.com/microsoft/playwright/pull/1911/checks?check_run_id=607149016');
+  test.flaky(options.FIREFOX(parameters) && options.WIN(parameters), 'Occasionally times out on options.FIREFOX on Windows: https://github.com/microsoft/playwright/pull/1911/checks?check_run_id=607149016');
 }, async ({page, server}) => {
   await page.evaluate(() => {
     window['clickPromise'] = new Promise(resolve => {
@@ -123,12 +123,12 @@ it('should trigger hover state with removed window.Node', async ({page, server})
   expect(await page.evaluate(() => document.querySelector('button:hover').id)).toBe('button-6');
 });
 
-it('should set modifier keys on click', async ({page, server, isFirefox}) => {
+it('should set modifier keys on click', async ({page, server, isFirefox, isMac}) => {
   await page.goto(server.PREFIX + '/input/scrollable.html');
   await page.evaluate(() => document.querySelector('#button-3').addEventListener('mousedown', e => window['lastEvent'] = e, true));
   const modifiers = {'Shift': 'shiftKey', 'Control': 'ctrlKey', 'Alt': 'altKey', 'Meta': 'metaKey'};
   // In Firefox, the Meta modifier only exists on Mac
-  if (isFirefox && !MAC)
+  if (isFirefox && !isMac)
     delete modifiers['Meta'];
   for (const modifier in modifiers) {
     await page.keyboard.down(modifier);
diff --git a/test/network-request.spec.ts b/test/network-request.spec.ts
index a2f9133ede..0f3068000c 100644
--- a/test/network-request.spec.ts
+++ b/test/network-request.spec.ts
@@ -56,7 +56,7 @@ it('should return headers', async ({page, server, isChromium, isFirefox, isWebKi
 });
 
 it('should get the same headers as the server', (test, parameters) => {
-  test.fail(options.CHROMIUM(parameters) || options.WEBKIT(parameters));
+  test.fail(options.CHROMIUM(parameters) || options.WEBKIT(parameters), 'Provisional headers differ from those in network stack');
 }, async ({page, server}) => {
   await page.goto(server.PREFIX + '/empty.html');
   let serverRequest;
diff --git a/test/page-event-crash.spec.ts b/test/page-event-crash.spec.ts
index ebe42aeb3b..bb41b8b297 100644
--- a/test/page-event-crash.spec.ts
+++ b/test/page-event-crash.spec.ts
@@ -28,7 +28,7 @@ function crash(page, toImpl, browserName) {
 
 describe('', (suite, parameters) => {
   suite.fixme(options.WIRE);
-  suite.flaky(options.FIREFOX(parameters) && WIN);
+  suite.flaky(options.FIREFOX(parameters) && options.WIN(parameters));
 }, () => {
   it('should emit crash event when page crashes', async ({page, browserName, toImpl}) => {
     await page.setContent(`<div>This page should crash</div>`);
@@ -65,7 +65,7 @@ describe('', (suite, parameters) => {
 
   it('should be able to close context when page crashes', (test, parameters) => {
     test.fixme(options.WIRE);
-    test.flaky(options.FIREFOX(parameters) && WIN);
+    test.flaky(options.FIREFOX(parameters) && options.WIN(parameters));
   }, async ({page, browserName, toImpl}) => {
     await page.setContent(`<div>This page should crash</div>`);
     crash(page, toImpl, browserName);
diff --git a/test/page-event-network.spec.ts b/test/page-event-network.spec.ts
index 65b04525b7..9aad1658f9 100644
--- a/test/page-event-network.spec.ts
+++ b/test/page-event-network.spec.ts
@@ -41,7 +41,7 @@ it('Page.Events.Response', async ({page, server}) => {
   expect(responses[0].request()).toBeTruthy();
 });
 
-it('Page.Events.RequestFailed', async ({page, server, isChromium, isWebKit}) => {
+it('Page.Events.RequestFailed', async ({page, server, isChromium, isWebKit, isMac, isWindows}) => {
   server.setRoute('/one-style.css', (req, res) => {
     res.setHeader('Content-Type', 'text/css');
     res.connection.destroy();
@@ -56,9 +56,9 @@ it('Page.Events.RequestFailed', async ({page, server, isChromium, isWebKit}) =>
   if (isChromium) {
     expect(failedRequests[0].failure().errorText).toBe('net::ERR_EMPTY_RESPONSE');
   } else if (isWebKit) {
-    if (MAC)
+    if (isMac)
       expect(failedRequests[0].failure().errorText).toBe('The network connection was lost.');
-    else if (WIN)
+    else if (isWindows)
       expect(failedRequests[0].failure().errorText).toBe('Server returned nothing (no headers, no data)');
     else
       expect(failedRequests[0].failure().errorText).toBe('Message Corrupt');
diff --git a/test/page-goto.spec.ts b/test/page-goto.spec.ts
index ab4ccf3ad3..83e8d1637d 100644
--- a/test/page-goto.spec.ts
+++ b/test/page-goto.spec.ts
@@ -210,12 +210,12 @@ it('should throw if networkidle2 is passed as an option', async ({page, server})
   expect(error.message).toContain(`waitUntil: expected one of (load|domcontentloaded|networkidle)`);
 });
 
-it('should fail when main resources failed to load', async ({page, isChromium, isWebKit}) => {
+it('should fail when main resources failed to load', async ({page, isChromium, isWebKit, isWindows}) => {
   let error = null;
   await page.goto('http://localhost:44123/non-existing-url').catch(e => error = e);
   if (isChromium)
     expect(error.message).toContain('net::ERR_CONNECTION_REFUSED');
-  else if (isWebKit && WIN)
+  else if (isWebKit && isWindows)
     expect(error.message).toContain(`Couldn\'t connect to server`);
   else if (isWebKit)
     expect(error.message).toContain('Could not connect');
diff --git a/test/page-history.spec.ts b/test/page-history.spec.ts
index 2b3ecc5028..db4ee444f4 100644
--- a/test/page-history.spec.ts
+++ b/test/page-history.spec.ts
@@ -53,7 +53,7 @@ it('page.goBack should work with HistoryAPI', async ({page, server}) => {
 });
 
 it('page.goBack should work for file urls', (test, parameters) => {
-  test.fail(options.WEBKIT(parameters) && MAC);
+  test.fail(options.WEBKIT(parameters) && options.MAC(parameters));
 }, async ({page, server, asset}) => {
   // WebKit embedder fails to go back/forward to the file url.
   const url1 = url.pathToFileURL(asset('empty.html')).href;
diff --git a/test/page-screenshot.spec.ts b/test/page-screenshot.spec.ts
index 80ad73c111..ded991cd53 100644
--- a/test/page-screenshot.spec.ts
+++ b/test/page-screenshot.spec.ts
@@ -219,7 +219,7 @@ describe('page screenshot', (suite, parameters) => {
 
   it('should work for webgl', (test, parameters) => {
     test.fixme(options.FIREFOX(parameters));
-    test.fixme(options.WEBKIT(parameters) && LINUX);
+    test.fixme(options.WEBKIT(parameters) && options.LINUX(parameters));
   }, async ({page, server, golden}) => {
     await page.setViewportSize({width: 640, height: 480});
     await page.goto(server.PREFIX + '/screenshots/webgl.html');
diff --git a/test/permissions.spec.ts b/test/permissions.spec.ts
index efb1dcd9af..3cd4bd5ab5 100644
--- a/test/permissions.spec.ts
+++ b/test/permissions.spec.ts
@@ -104,7 +104,7 @@ describe('permissions', (suite, parameters) => {
   it('should trigger permission onchange', (test, parameters) => {
     test.fail(options.WEBKIT(parameters));
     test.fail(options.CHROMIUM(parameters) && !options.HEADLESS);
-    test.flaky(options.FIREFOX(parameters) && LINUX);
+    test.flaky(options.FIREFOX(parameters) && options.LINUX(parameters));
   }, async ({page, server, context}) => {
     // TODO: flaky
     // - Linux: https://github.com/microsoft/playwright/pull/1790/checks?check_run_id=587327883
diff --git a/test/playwright.fixtures.ts b/test/playwright.fixtures.ts
index 8dc5434398..92413cdc3e 100644
--- a/test/playwright.fixtures.ts
+++ b/test/playwright.fixtures.ts
@@ -25,8 +25,10 @@ import { Transport } from '../lib/protocol/transport';
 import { installCoverageHooks } from './coverage';
 import { mkdtempAsync, removeFolderAsync } from './utils';
 import { fixtures as baseFixtures } from '@playwright/test-runner';
+import assert from 'assert';
 
 type PlaywrightParameters = {
+  platform: 'win32' | 'linux' | 'darwin'
   browserName: string;
 };
 
@@ -43,6 +45,9 @@ type PlaywrightWorkerFixtures = {
   isChromium: boolean;
   isFirefox: boolean;
   isWebKit: boolean;
+  isWindows: boolean;
+  isMac: boolean;
+  isLinux: boolean;
 };
 
 type PlaywrightFixtures = {
@@ -74,9 +79,12 @@ export const afterAll = fixtures.afterAll;
 export const expect = fixtures.expect;
 
 export const options = {
-  CHROMIUM: parameters => parameters.browserName === 'chromium',
-  FIREFOX: parameters => parameters.browserName === 'firefox',
-  WEBKIT: parameters => parameters.browserName === 'webkit',
+  CHROMIUM: (parameters: PlaywrightParameters) => parameters.browserName === 'chromium',
+  FIREFOX: (parameters: PlaywrightParameters) => parameters.browserName === 'firefox',
+  WEBKIT: (parameters: PlaywrightParameters) => parameters.browserName === 'webkit',
+  MAC: (parameters: PlaywrightParameters) => parameters.platform === 'darwin',
+  LINUX: (parameters: PlaywrightParameters) => parameters.platform === 'linux',
+  WIN: (parameters: PlaywrightParameters) => parameters.platform === 'win32',
   HEADLESS: !!valueFromEnv('HEADLESS', true),
   WIRE: !!process.env.PWWIRE,
   SLOW_MO: valueFromEnv('SLOW_MO', 0),
@@ -84,16 +92,6 @@ export const options = {
   TRACING: valueFromEnv('TRACING', false) && !process.env.PWWIRE,
 };
 
-declare global {
-  const MAC: boolean;
-  const LINUX: boolean;
-  const WIN: boolean;
-}
-const platform = os.platform();
-global['MAC'] = platform === 'darwin';
-global['LINUX'] = platform === 'linux';
-global['WIN'] = platform === 'win32';
-
 defineWorkerFixture('httpService', async ({parallelIndex}, test) => {
   const assetsPath = path.join(__dirname, 'assets');
   const cachedPath = path.join(__dirname, 'assets', 'cached');
@@ -136,7 +134,8 @@ defineWorkerFixture('defaultBrowserOptions', async ({browserName}, test) => {
   });
 });
 
-defineWorkerFixture('playwright', async ({browserName, parallelIndex}, test) => {
+defineWorkerFixture('playwright', async ({browserName, parallelIndex, platform}, test) => {
+  assert(platform); // Depend on platform to generate all tests.
   const {coverage, uninstall} = installCoverageHooks(browserName);
   if (options.WIRE) {
     require('../lib/utils/utils').setUnderTest();
@@ -192,10 +191,15 @@ defineWorkerFixture('browserType', async ({playwright, browserName}, test) => {
 
 defineParameter('browserName', 'Browser type name', '');
 
+defineParameter('platform', 'Operating system', process.platform as ('win32' | 'linux' | 'darwin'));
+
 generateParametrizedTests(
     'browserName',
     process.env.BROWSER ? [process.env.BROWSER] : ['chromium', 'webkit', 'firefox']);
 
+generateParametrizedTests(
+    'platform',
+    process.env.PWTESTREPORT ? ['win32', 'darwin', 'linux'] : [process.platform as ('win32' | 'linux' | 'darwin')]);
 
 defineWorkerFixture('isChromium', async ({browserName}, test) => {
   await test(browserName === 'chromium');
@@ -209,6 +213,18 @@ defineWorkerFixture('isWebKit', async ({browserName}, test) => {
   await test(browserName === 'webkit');
 });
 
+defineWorkerFixture('isWindows', async ({platform}, test) => {
+  await test(platform === 'win32');
+});
+
+defineWorkerFixture('isMac', async ({platform}, test) => {
+  await test(platform === 'darwin');
+});
+
+defineWorkerFixture('isLinux', async ({platform}, test) => {
+  await test(platform === 'linux');
+});
+
 defineWorkerFixture('browser', async ({browserType, defaultBrowserOptions}, test) => {
   const browser = await browserType.launch(defaultBrowserOptions);
   await test(browser);
diff --git a/test/proxy.spec.ts b/test/proxy.spec.ts
index 686470be39..be413b5a4b 100644
--- a/test/proxy.spec.ts
+++ b/test/proxy.spec.ts
@@ -120,7 +120,7 @@ it('should exclude patterns', (test, parameters) => {
 });
 
 it('should use socks proxy', (test, parameters) => {
-  test.flaky(MAC && options.WEBKIT(parameters), 'Intermittent page.goto: The network connection was lost error on bots');
+  test.flaky(options.MAC(parameters) && options.WEBKIT(parameters), 'Intermittent page.goto: The network connection was lost error on bots');
 }, async ({ browserType, defaultBrowserOptions, parallelIndex }) => {
   const server = socks.createServer((info, accept, deny) => {
     let socket;
diff --git a/test/screencast.spec.ts b/test/screencast.spec.ts
index e3281a7610..0407ce1ee7 100644
--- a/test/screencast.spec.ts
+++ b/test/screencast.spec.ts
@@ -249,7 +249,7 @@ describe('screencast', suite => {
   });
 
   it('should capture css transformation', (test, parameters) => {
-    test.fail(options.WEBKIT(parameters) && WIN, 'Does not work on WebKit Windows');
+    test.fail(options.WEBKIT(parameters) && options.WIN(parameters), 'Does not work on WebKit Windows');
   }, async ({browser, server, videoPlayer, videoFile}) => {
     const size = {width: 320, height: 240};
     // Set viewport equal to screencast frame size to avoid scaling.