[dashboard] adding an option to duplicate slices when "Saving AS" (#3391)

* [dashboard] adding an option to duplicate slices when "Saving AS"

* Fix tests

superset/assets/spec/javascripts/components/Checkbox_spec.jsx

@@ -0,0 +1,39 @@
+import React from 'react';
+import { expect } from 'chai';
+import { describe, it } from 'mocha';
+import sinon from 'sinon';
+import { shallow } from 'enzyme';
+
+import Checkbox from '../../../javascripts/components/Checkbox';
+
+describe('Checkbox', () => {
+  const defaultProps = {
+    checked: true,
+    onChange: sinon.spy(),
+  };
+
+  let wrapper;
+  const factory = (o) => {
+    const props = Object.assign({}, defaultProps, o);
+    return shallow(<Checkbox {...props} />);
+  };
+  beforeEach(() => {
+    wrapper = factory({});
+  });
+  it('is a valid element', () => {
+    expect(React.isValidElement(<Checkbox {...defaultProps} />)).to.equal(true);
+  });
+  it('inits checked when checked', () => {
+    expect(wrapper.find('i.fa-check.text-primary')).to.have.length(1);
+  });
+  it('inits unchecked when not checked', () => {
+    const el = factory({ checked: false });
+    expect(el.find('i.fa-check.text-primary')).to.have.length(0);
+    expect(el.find('i.fa-check.text-transparent')).to.have.length(1);
+  });
+  it('unchecks when clicked', () => {
+    expect(wrapper.find('i.fa-check.text-transparent')).to.have.length(0);
+    wrapper.find('i').first().simulate('click');
+    expect(defaultProps.onChange.calledOnce).to.equal(true);
+  });
+});