[dashboard v2] add MissingChart component in the case that chart component has no slice definition, add tests. (#5296)

superset/assets/spec/javascripts/dashboard/components/MissingChart_spec.jsx

@@ -0,0 +1,29 @@
+import React from 'react';
+import { shallow } from 'enzyme';
+import { describe, it } from 'mocha';
+import { expect } from 'chai';
+
+import Loading from '../../../../src/components/Loading';
+import MissingChart from '../../../../src/dashboard/components/MissingChart';
+
+describe('MissingChart', () => {
+  function setup(overrideProps) {
+    const wrapper = shallow(<MissingChart height={100} {...overrideProps} />);
+    return wrapper;
+  }
+
+  it('renders a .missing-chart-container', () => {
+    const wrapper = setup();
+    expect(wrapper.find('.missing-chart-container')).to.have.length(1);
+  });
+
+  it('renders a .missing-chart-body', () => {
+    const wrapper = setup();
+    expect(wrapper.find('.missing-chart-body')).to.have.length(1);
+  });
+
+  it('renders a Loading', () => {
+    const wrapper = setup();
+    expect(wrapper.find(Loading)).to.have.length(1);
+  });
+});