What features should be considered when testing individual microservices modularly?

When performing unit testing of microservices, it is important to consider:

• Isolation of the tested microservice: tests should verify only the functionality of the specific service, without dependence on other services.
• Mocking external calls: interactions with other microservices or external systems should be replaced with mocks or stubs to avoid affecting the tests.
• API and contract testing: verify the correctness of input and output data, and compliance with contracts.
• Handling asynchrony and events: if the microservice processes events or operates asynchronously, tests should account for this correctly.
• Automation and repeatability: tests should be automated and produce stable results upon repeated runs.

Example: when testing a service that calls another microservice, use a mock that returns a predefined response instead of a real call.