Explain the positives and negatives of shallow rendering components in tests.

Positives:

• It is faster to shallow render a component than to fully render it. When a React project contains a large number of components, this performance difference can have a significant impact on the total time taken for unit tests to execute.
• Shallow rendering prevents testing outside the boundaries of the component being tested—a best practice of unit testing.

Negatives:

• Shallow rendering is less similar to real-world usage of a component as part of an application, so it may not catch certain problems. Take the example of a <House /> component that renders a <LivingRoom /> component. Within a real application, if the <LivingRoom /> component is broken and throws an error, then <House /> would fail to render. However, if the unit tests of <House /> only use shallow rendering, then this issue will not be identified unless <LivingRoom /> is also covered with unit tests.