improvement: flow coverage

src/templates/tag-template.test.js

@@ -1,3 +1,4 @@
+// @flow
 import React from 'react';
 import renderer from 'react-test-renderer';
 import { useStaticQuery, StaticQuery } from 'gatsby';
@@ -5,11 +6,12 @@ import TagTemplate from './tag-template';
 import siteMetadata from '../../jest/__fixtures__/site-metadata';
 import allMarkdownRemark from '../../jest/__fixtures__/all-markdown-remark';
 import pageContext from '../../jest/__fixtures__/page-context';
+import type { RenderCallback } from '../types';
 
 describe('TagTemplate', () => {
   beforeEach(() => {
     StaticQuery.mockImplementationOnce(
-      ({ render }) => (
+      ({ render }: RenderCallback) => (
         render(siteMetadata)
       ),
       useStaticQuery.mockReturnValue(siteMetadata)