[js-testing] add tests for explore actions (#2976)

* move to explore folder and delete explorev2 folder

* add tests for fetchDatasourceMetadata

* tests for fetchDatasources, fetchDatasourceMetadata

* use $.ajax for fetch dashboards and write test

superset/assets/spec/javascripts/explore/components/BoundsControl_spec.jsx

@@ -0,0 +1,38 @@
+/* eslint-disable no-unused-expressions */
+import React from 'react';
+import { FormControl } from 'react-bootstrap';
+import sinon from 'sinon';
+import { expect } from 'chai';
+import { describe, it, beforeEach } from 'mocha';
+import { mount } from 'enzyme';
+
+import BoundsControl from '../../../../javascripts/explore/components/controls/BoundsControl';
+
+const defaultProps = {
+  name: 'y_axis_bounds',
+  label: 'Bounds of the y axis',
+  onChange: sinon.spy(),
+};
+
+describe('BoundsControl', () => {
+  let wrapper;
+
+  beforeEach(() => {
+    wrapper = mount(<BoundsControl {...defaultProps} />);
+  });
+
+  it('renders two FormControls', () => {
+    expect(wrapper.find(FormControl)).to.have.lengthOf(2);
+  });
+
+  it('errors on non-numeric', () => {
+    wrapper.find(FormControl).first().simulate('change', { target: { value: 's' } });
+    expect(defaultProps.onChange.calledWith([null, null])).to.be.true;
+    expect(defaultProps.onChange.getCall(0).args[1][0]).to.contain('value should be numeric');
+  });
+  it('casts to numeric', () => {
+    wrapper.find(FormControl).first().simulate('change', { target: { value: '1' } });
+    wrapper.find(FormControl).last().simulate('change', { target: { value: '5' } });
+    expect(defaultProps.onChange.calledWith([1, 5])).to.be.true;
+  });
+});