feat: add "clearSession" browser command

README.md

@@ -385,6 +385,30 @@ Finally, run tests (be sure that you have already run `selenium-standalone start
 node_modules/.bin/hermione
 ```
 
+## Commands API
+
+Since Hermione is based on [WebdriverIO v8](https://webdriver.io/docs/api/), all the commands provided by WebdriverIO are available in it. But Hermione also has her own commands.
+
+### clearSession
+
+Browser command that clear session state (delete cookies, clear local and session storages). For example:
+
+```js
+it('', async ({ browser }) => {
+    await browser.url('https://github.com/gemini-testing/hermione');
+
+    (await browser.getCookies()).length; // 5
+    await browser.execute(() => localStorage.length); // 2
+    await browser.execute(() => localStorage.length); // 1
+
+    await browser.clearSession();
+
+    (await browser.getCookies()).length; // 0
+    await browser.execute(() => localStorage.length); // 0
+    await browser.execute(() => localStorage.length); // 0
+});
+```
+
 ## Tests API
 
 ### Arguments
@@ -1640,8 +1664,6 @@ Another command features:
     // foo: 1
     ```
 
-
-
 #### Test development in runtime
 
 For quick test development without restarting the test or the browser, you can run the test in the terminal of IDE with enabled REPL mode:
@@ -1652,6 +1674,10 @@ npx hermione --repl-before-test --grep "foo" -b "chrome"
 
 After that, you need to configure the hotkey in IDE to run the selected one or more lines of code in the terminal. As a result, each new written line can be sent to the terminal using a hotkey and due to this, you can write a test much faster.
 
+Also, during the test development process, it may be necessary to execute commands in a clean environment (without side effects from already executed commands). To do this, you can use the following commands:
+- [clearSession](#clearsession) - clear session state (delete cookies, clear local and session storages). in some cases, the environment may contain side effects from already executed commands;
+- [reloadSession](https://webdriver.io/docs/api/browser/reloadSession/) - creates a new session with a completely clean environment.
+
 ##### How to set up using VSCode
 
 1. Open `Code` -> `Settings...` -> `Keyboard Shortcuts` and print `run selected text` to search input. After that, you can specify the desired key combination

src/browser/commands/clearSession.ts

@@ -0,0 +1,27 @@
+import type { Browser } from "../types";
+import logger from "../../utils/logger";
+
+export = async (browser: Browser): Promise<void> => {
+    const { publicAPI: session } = browser;
+
+    const clearStorage = async (storageName: "localStorage" | "sessionStorage"): Promise<void> => {
+        try {
+            await session.execute(storageName => window[storageName].clear(), storageName);
+        } catch (e) {
+            const message = (e as Error).message || "";
+
+            if (message.startsWith(`Failed to read the '${storageName}' property from 'Window'`)) {
+                logger.warn(`Couldn't clear ${storageName}: ${message}`);
+            } else {
+                throw e;
+            }
+        }
+    };
+
+    session.addCommand("clearSession", async function (): Promise<void> {
+        await session.deleteAllCookies();
+
+        await clearStorage("localStorage");
+        await clearStorage("sessionStorage");
+    });
+};

src/browser/commands/index.js

@@ -2,6 +2,7 @@
 
 module.exports = [
     "assert-view",
+    "clearSession",
     "getConfig",
     "getPuppeteer",
     "setOrientation",

test/src/browser/commands/clearSession.ts

@@ -0,0 +1,92 @@
+import webdriverio from "webdriverio";
+import sinon, { SinonStub } from "sinon";
+
+import clientBridge from "src/browser/client-bridge";
+import logger from "src/utils/logger";
+import { mkExistingBrowser_ as mkBrowser_, mkSessionStub_ } from "../utils";
+
+import type ExistingBrowser from "src/browser/existing-browser";
+
+describe('"clearSession" command', () => {
+    const sandbox = sinon.sandbox.create();
+
+    const initBrowser_ = ({ browser = mkBrowser_(), session = mkSessionStub_() } = {}): Promise<ExistingBrowser> => {
+        (webdriverio.attach as SinonStub).resolves(session);
+
+        return browser.init({ sessionId: session.sessionId, sessionCaps: session.capabilities, sessionOpts: {} });
+    };
+
+    beforeEach(() => {
+        sandbox.stub(webdriverio, "attach");
+        sandbox.stub(clientBridge, "build").resolves();
+        sandbox.stub(logger, "warn");
+
+        global.window = {
+            localStorage: { clear: sinon.stub() } as unknown as Storage,
+            sessionStorage: { clear: sinon.stub() } as unknown as Storage,
+        } as unknown as Window & typeof globalThis;
+    });
+
+    afterEach(() => {
+        global.window = undefined as unknown as Window & typeof globalThis;
+        sandbox.restore();
+    });
+
+    it("should add command", async () => {
+        const session = mkSessionStub_();
+
+        await initBrowser_({ session });
+
+        assert.calledWith(session.addCommand, "clearSession", sinon.match.func);
+    });
+
+    it("should delete all cookies", async () => {
+        const session = mkSessionStub_();
+
+        await initBrowser_({ session });
+        await session.clearSession();
+
+        assert.calledOnce(session.deleteAllCookies);
+    });
+
+    ["localStorage", "sessionStorage"].forEach(storageName => {
+        describe(storageName, () => {
+            it("should clear", async () => {
+                const session = mkSessionStub_();
+                session.execute.callsFake((cb: (storageName: string) => void, storageName: string) => cb(storageName));
+
+                await initBrowser_({ session });
+                await session.clearSession();
+
+                assert.calledOnce(global.window[storageName].clear);
+            });
+
+            it("should not throw is storage is not available on the page", async () => {
+                const err = new Error(
+                    `Failed to read the '${storageName}' property from 'Window': Storage is disabled inside 'data:' URLs.`,
+                );
+                global.window[storageName].clear.throws(err);
+
+                const session = mkSessionStub_();
+                session.execute.callsFake((cb: (storageName: string) => void, storageName: string) => cb(storageName));
+
+                await initBrowser_({ session });
+
+                await assert.isFulfilled(session.clearSession());
+                assert.calledOnceWith(logger.warn, `Couldn't clear ${storageName}: ${err.message}`);
+            });
+
+            it("should throw if clear storage fails with not handled error", async () => {
+                const err = new Error("o.O");
+                global.window[storageName].clear.throws(err);
+
+                const session = mkSessionStub_();
+                session.execute.callsFake((cb: (storageName: string) => void, storageName: string) => cb(storageName));
+
+                await initBrowser_({ session });
+
+                await assert.isRejected(session.clearSession(), /o.O/);
+            });
+        });
+    });
+});

test/src/browser/utils.js

@@ -112,6 +112,7 @@ exports.mkSessionStub_ = () => {
     session.switchToFrame = sinon.stub().named("switchToFrame").resolves();
     session.switchToParentFrame = sinon.stub().named("switchToParentFrame").resolves();
     session.switchToRepl = sinon.stub().named("switchToRepl").resolves();
+    session.deleteAllCookies = sinon.stub().named("deleteAllCookies").resolves();
 
     session.addCommand = sinon.stub().callsFake((name, command, isElement) => {
         const target = isElement ? wdioElement : session;