Jasmine beforeEach() Function

The Jasmine beforeEach() function allows you to execute some code before the spec in the it() block.

In Neil Gaiman's fantasy novel Stardust, there is a wall which divides England and the magical kingdom of Stormhold. Our hero of the story Tristan has to enter Stormhold to go get a fallen star.

We create a test suite where the variable tristan is initialized to 'England'. We expect the variable tristan to take the value 'Stormhold' inside the setTimeout() function after 1.5 seconds

				
				describe('Tristan Thorn', function() {
				  	var tristan = 'England';
				  
				   	setTimeout(function() {
					  tristan = 'Stormhold';	  
					}, 1500);

				  	it('is in Stormhold', function() {
				    	expect(tristan).toEqual('Stormhold');
				  	});
				});
				
			

The test fails because the it() block is executed before completion of the setTimeout() operation, and the tristan variable still holds the initial value 'England'.

Async operations (as in the example above) goes inside the beforeEach() function, to which the done() function is passed as an argument causing Jasmine to wait until it is called before executing the spec in the it() block. The test suite can now be rewritten as

				
				describe('Tristan Thorn', function() {
				  	var tristan = 'England';

				  	beforeEach(function(done) {
					    setTimeout(function() {
					      tristan = 'Stormhold';
					      done();
					    }, 1500);
				  	});

				  	it('is in Stormhold', function() {
					    expect(tristan).toEqual('Stormhold');
				  	});
				});
				
			

This time, the spec passes. On running the spec configured in Grunt, the output to the terminal looks like