Javascript Jasmine检查数组是否为空-fabric js未定义

我开始使用Jasmine对我的代码运行测试。到目前为止，大多数测试都相当原始，但我现在在检查数组是否已填充时遇到了一个问题

测试是：

describe("create grid of layers", function() {
    var result = new Array(4);
    it("returns an array of objects as a grid", function() {
        result = randomQuadrants();
        expect( result).toBeDefined();
    });
});

我也试过：

describe("create grid of layers", function() {
    var result = new Array(4);
    it("returns an array of objects as a grid", function() {
        expect(result = randomQuadrants()).toBeDefined();
    });
});

同样，但我收到一个错误，即ReferenceError:fabric未在以下代码中的这一行定义var obj=new fabric.GeologicalObject{

function randomQuadrants() {
    var posX, posY;
    posY = 175;

    for (var i=0; i<10; i++){
        //declaring random num here makes each layer the same but random.
        grid[i] = new Array(6);
        posX = 100;

        for(j=0; j<10; j++) {
            //random num here makes each square a random layer
            var randomNum = random_num(layerDetails.length);
            var obj = new fabric.GeologicalObject({
                strength: layerDetails[randomNum].strength,
                minSpeed: layerDetails[randomNum].minSpeed ,
                maxSpeed: layerDetails[randomNum].maxSpeed,
                width: 200,
                height: 75,
                left:  posX,
                top: posY,
                fill: 'red'
            });

            posX = parseInt(posX) + 200;
            loadPattern(obj, layerDetails[randomNum].pattern);
            grid[i][j] = obj;
        }
        posY+=75;
    }
    return grid;
}

谢谢你的帮助