In my real code, I encountered a problem that I wanted to demonstrate with a simple example.
The code below functions properly. I defined a variable in the root describe() block that can be accessed in the it() blocks of nested describe()s.
describe('simple object', function () {
var orchard;
beforeEach(function () {
orchard = {
trees: {
apple: 10,
orange : 20
},
bushes: {
boysenberry : 40,
blueberry: 35
}
};
});
describe('trees', function () {
it ('should have apples and oranges', function() {
var trees = orchard.trees;
expect (trees.apple).toBeDefined();
expect (trees.orange).toBeDefined();
expect (trees.apple).toEqual(10);
expect (trees.orange).toEqual(20);
});
it ('should NOT have pears or cherries', function() {
var trees = orchard.trees;
expect (trees.pear).toBeUndefined();
expect (trees.cherry).toBeUndefined();
});
});
});
However, when I attempted to refactor my code to make it more concise, the following approach failed:
describe('simple object', function () {
var orchard;
beforeEach(function () {
orchard = {
trees: {
apple: 10,
orange : 20
},
bushes: {
boysenberry : 40,
blueberry: 35
}
};
});
describe('trees', function () {
var trees = orchard.trees; // TypeError: Cannot read property 'trees' of undefined
it ('should have apples and oranges', function() {
expect (trees.apple).toBeDefined();
expect (trees.orange).toBeDefined();
expect (trees.apple).toEqual(10);
expect (trees.orange).toEqual(20);
});
it ('should NOT have pears or cherries', function() {
expect (trees.pear).toBeUndefined();
expect (trees.cherry).toBeUndefined();
});
});
});
Inside the nested describe(), the orchard object is undefined, even though it's defined within the it() blocks inside it.
Was this intentional by Jasmine's developers to prevent issues with resetting the object in beforeEach()? How does it work? It seems like some sort of magic with apply() or call(), but I'm unsure...
--
On a related note, I can still streamline my code by adding another beforeEach() block:
describe('simple object', function () {
var orchard;
beforeEach(function () {
orchard = {
trees: {
apple: 10,
orange : 20
},
bushes: {
boysenberry : 40,
blueberry: 35
}
};
});
describe('trees', function () {
var trees;
beforeEach(function() {
trees = orchard.trees;
});
it ('should have apples and oranges', function() {
expect (trees.apple).toBeDefined();
expect (trees.orange).toBeDefined();
expect (trees.apple).toEqual(10);
expect (trees.orange).toEqual(20);
});
it ('should NOT have pears or cherries', function() {
expect (trees.pear).toBeUndefined();
expect (trees.cherry).toBeUndefined();
});
});
});