How do you unit-test a Spring service without loading ApplicationContext?

Constructs a service directly with explicit collaborators and verifies behavior without Spring startup or framework-owned concerns.

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TL;DR

I instantiate the service directly in a JUnit test and pass its constructor dependencies as small fakes, stubs, or Mockito mocks. The test calls the public operation and asserts the returned value, state change, or meaningful collaboration. No @SpringBootTest, Spring extension, or component scan is needed. Constructor injection makes the required setup visible and keeps the test fast.

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Constructor injection, JUnit, Mockito or fakes, behavior assertions, collaboration boundaries, and test speed.

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Overview
A class annotated with @Service is still an ordinary Java object when its behavior does not require Spring infrastructure.
I instantiate the service directly in a JUnit test and pass its constructor dependencies as small fakes, stubs, or Mockito mocks. The test calls the public operation and asserts the returned value, state change, or meaningful collaboration. No @SpringBootTest, Spring extension, or component scan is needed. Constructor injection makes the required setup visible and keeps the test fast.
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I prefer state or outcome assertions and verify interactions only when the collaboration itself is the contract, such as publishing one command after a successful save. I avoid mocking value objects, collections, and the service under test. Framework behavior such as , validation proxies, caching, or method security is not active in this unit test; those concerns need a focused integration test rather than pretending the annotation ran.

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Loading the whole application for ordinary branch logic.
Mocking the class under test.
Assuming transactional or security annotations execute in a direct unit test.

How do you unit-test a Spring service without loading ApplicationContext?

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