包装器引用丢失

Question

在这些代码行之后，我可以成功访问我的包装器和实例：

containerDiv.style.width = '400px';
global.document.body.appendChild(containerDiv);

wrapper2 = mount(
    <DocumentList 
        oid={'docOid251085'}/>,
    {attachTo: containerDiv}
);
instance2 = wrapper2.component.getInstance();

wrapper = mount(
    <DocumentListRow 
        getDocumentListWidth={instance2.getDocumentListWidth}
        oid={'docOid251085'}
        record={record}/>,
    {attachTo: document.getElementById('DocumentGriddocOid251085')}
);
instance = wrapper.component.getInstance();

但是在下一个“it”块中，我无法访问它们，是什么让我失去了包装器和实例引用？

it("should render one row", function() {
    expect(wrapper.find('Row_1_' + 'docOid251085')).to.exist;
});

it("should render one row in a card that is normal", function() {
    var width;

    width = instance.props.getDocumentListWidth();

    expect(width).to.equal(400);
});