Update remaining collections

collections/react/rendering.yaml

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+slug: react/rendering
+name: React Rendering
+miniName: Rendering
+parent: react
+featured: true
+snippetIds:
+  - articles/s/react-rendering-basics
+  - articles/s/react-rendering-optimization
+  - articles/s/react-rendering-state
+splash: glasses-comic.png
+description: >-
+  Understanding of the rendering process is a crucial piece of knowledge when
+  creating web applications with React. Take a deep dive into the fundamentals
+  and core concepts as well as more advanced techniques with this series of
+  articles.
+shortDescription: >-
+  Understand the fundamentals of React's rendering process as well as more
+  advanced techniques with this series of articles.

collections/react/testing.yaml

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+slug: react/testing
+name: React Testing
+shortName: Testing
+parent: react
+featured: true
+snippetIds:
+  - articles/s/testing-stateful-ui-components
+  - articles/s/testing-async-react-components
+  - articles/s/testing-react-portals
+  - articles/s/testing-redux-connected-components
+splash: headphones.png
+description: >-
+  Testing React can be challenging, both in terms of figuring out the correct
+  mentality as well as understanding the mechanics of the tools you're working
+  with. This article collection aims to teach you the basics of testing React
+  components in various scenarios using React Testing Library.
+shortDescription: >-
+  Learn some of the basics of testing React components in various scenarios
+  using React Testing Library.