Fix failing location tests

- By adding a new useLocation mock
+ add SideNavLink active class test

TODO: I should probably rename react_router_history.mock to just react_router.mock

x-pack/plugins/enterprise_search/public/applications/__mocks__/index.ts

@@ -4,7 +4,7 @@
  * you may not use this file except in compliance with the Elastic License.
  */
 
-export { mockHistory } from './react_router_history.mock';
+export { mockHistory, mockLocation } from './react_router_history.mock';
 export { mockKibanaContext } from './kibana_context.mock';
 export { mockLicenseContext } from './license_context.mock';
 export {

x-pack/plugins/enterprise_search/public/applications/__mocks__/react_router_history.mock.ts

@@ -5,7 +5,7 @@
  */
 
 /**
- * NOTE: This variable name MUST start with 'mock*' in order for
+ * NOTE: These variable names MUST start with 'mock*' in order for
  * Jest to accept its use within a jest.mock()
  */
 export const mockHistory = {
@@ -15,9 +15,17 @@ export const mockHistory = {
     pathname: '/current-path',
   },
 };
+export const mockLocation = {
+  key: 'someKey',
+  pathname: '/current-path',
+  search: '?query=something',
+  hash: '#hash',
+  state: {},
+};
 
 jest.mock('react-router-dom', () => ({
   useHistory: jest.fn(() => mockHistory),
+  useLocation: jest.fn(() => mockLocation),
 }));
 
 /**

x-pack/plugins/enterprise_search/public/applications/shared/layout/side_nav.test.tsx

@@ -4,7 +4,10 @@
  * you may not use this file except in compliance with the Elastic License.
  */
 
+import '../../__mocks__/react_router_history.mock';
+
 import React from 'react';
+import { useLocation } from 'react-router-dom';
 import { shallow } from 'enzyme';
 
 import { EuiLink as EuiLinkExternal } from '@elastic/eui';
@@ -56,6 +59,26 @@ describe('SideNavLink', () => {
     expect(externalLink.prop('target')).toEqual('_blank');
   });
 
+  it('sets an active class if the current path matches the nav link', () => {
+    (useLocation as jest.Mock).mockImplementationOnce(() => ({ pathname: '/test/' }));
+
+    const wrapper = shallow(<SideNavLink to="/test">Link</SideNavLink>);
+
+    expect(wrapper.find('.enterpriseSearchNavLinks__item--isActive')).toHaveLength(1);
+  });
+
+  it('sets an active class if the current path is / and the link isRoot', () => {
+    (useLocation as jest.Mock).mockImplementationOnce(() => ({ pathname: '/' }));
+
+    const wrapper = shallow(
+      <SideNavLink to="/test" isRoot>
+        Link
+      </SideNavLink>
+    );
+
+    expect(wrapper.find('.enterpriseSearchNavLinks__item--isActive')).toHaveLength(1);
+  });
+
   it('passes down custom classes and props', () => {
     const wrapper = shallow(
       <SideNavLink to="/" className="testing" data-test-subj="testing">