Unit testing is crucial for ensuring that deployed cloud infrastructure aligns with expectations, such as verifying that resources' underlying assets have specific properties. Pulumi's unit testing framework, along with language-specific tools like introspection or filesystem calls, can be utilized to implement these tests effectively. Examples include checking that a cloud function's handler is executable, ensuring that a file's mime type matches the specified content type, and verifying that secrets are correctly marked and outputted as secret. These tests, which can be implemented in languages like Python, Node, .NET, and Go, help confirm the correctness of infrastructure components, such as AWS Lambda functions and S3 bucket objects, by validating executable functions, file types, and secret management. The use of Pulumi's testing capabilities allows developers to ensure that their cloud infrastructure is correctly configured and secure.