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    mock-local-storage

    1.1.17 • Public • Published

    Build Status

    mock-local-storage

    Mock localStorage for headless unit tests

    Inspired by StackOverflow answers and wrapped into npm package.

    Motivation

    Used to mock localStorage to run headless tests of cache implementation in terminal (ie. without browser).

    Installation

    npm install mock-local-storage --save-dev
    

    Usage

    Mocha

    Require in Mocha, which will replace localStorage and sessionStorage on the global and window objects:

    mocha --require mock-local-storage
    

    If you are using jsdom-global, make sure it is required before mock-local-storage:

    mocha --require jsdom-global --require mock-local-storage
    

    Other testing frameworks

    In a node environment you can mock the window.localStorage as follows:

    global.window = {}
    import 'mock-local-storage'
    window.localStorage = global.localStorage

    This is very useful when you want to run headless tests on code meant for the browser that use localStorage

    You can even store this in a file that is reused across tests:

    mock-localstorage.js

    global.window = {}
    import 'mock-local-storage'
    window.localStorage = global.localStorage

    using-localstorage.test.js

    import './mock-localstorage'
    
    // unit tests follow here

    Extra

    Besides mocking of conventional localStorage interface, this implementation provides a way for test code to register a callback to be invoked on item insertion. Mock implementation will invoke it when localStorage.setItem() is called (but not with localStorage[key] notation).

    It can be used to emulate allocation errors, like this:

    describe('test with mock localStorage', () => {
        afterEach(() => {
    	localStorage.clear();
    		// remove callback
    	localStorage.itemInsertionCallback = null;
        });
        it('emulate quota exceeded error', () => {
    	localStorage.length.should.equal(0);
    		// register callback
    	localStorage.itemInsertionCallback = (len) => {
    	    if (len >= 5) {
    		let err = new Error('Mock localStorage quota exceeded');
    		err.code = 22;
    		throw err;
    	    }
    	};
    	let handled = false;
    	try {
    	    for (let i = 0; i < 10; ++i) {
    		localStorage.setItem(i, i);
    	    }
    	} catch (e) {
    	    if (e.code == 22) {
    		// handle quota exceeded error
    		handled = true;
    	    }
    	}
    	handled.should.be.true;
    	localStorage.length.should.equal(5);
        });
    });

    Caveats

    There are some caveats with using index operator. Browser's localStorage works with strings and stringifyes objects stored via localStorage[key] notation, but this implementation does not.

    localStorage.itemInsertionCallback won't be invoked with localStorage[key] notation.

    Tests

    npm install
    npm test
    

    Bugs, issues, PRs, participation, contribution

    Please feel free to send us occusionall PRs along with unit tests, we'll merge them if they successfully build and pass unit tests. Consider to always provide unit tests, illustrating your problem, along with PR to avoid future regression.

    Note, that we currently do not use this project ourselves and cannot afford to invest much time into it. Please serve yourself.

    License

    MIT

    Install

    npm i mock-local-storage

    DownloadsWeekly Downloads

    68,375

    Version

    1.1.17

    License

    MIT

    Unpacked Size

    19.5 kB

    Total Files

    9

    Last publish

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