𝑇ℎ𝑒 𝑆𝑝𝑟𝑖𝑛𝑔𝐸𝑥𝑡𝑒𝑛𝑠𝑖𝑜𝑛 𝑓𝑎𝑐𝑖𝑙𝑖𝑡𝑎𝑡𝑒𝑠 𝑡ℎ𝑒 𝑠𝑚𝑜𝑜𝑡ℎ 𝑖𝑛𝑡𝑒𝑔𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝐽𝑈𝑛𝑖𝑡 𝐽𝑢𝑝𝑖𝑡𝑒𝑟 𝑡𝑒𝑠𝑡𝑠 𝑤𝑖𝑡ℎ 𝑆𝑝𝑟𝑖𝑛𝑔'𝑠 𝑇𝑒𝑠𝑡𝐶𝑜𝑛𝑡𝑒𝑥𝑡 𝑓𝑟𝑎𝑚𝑒𝑤𝑜𝑟𝑘.
𝐼𝑛 𝑚𝑜𝑠𝑡 𝑐𝑎𝑠𝑒𝑠, 𝑡ℎ𝑒𝑟𝑒 𝑖𝑠 𝑛𝑜 𝑛𝑒𝑒𝑑 𝑡𝑜 𝑚𝑎𝑛𝑢𝑎𝑙𝑙𝑦 𝑟𝑒𝑔𝑖𝑠𝑡𝑒𝑟 𝑡ℎ𝑒 𝑆𝑝𝑟𝑖𝑛𝑔𝐸𝑥𝑡𝑒𝑛𝑠𝑖𝑜𝑛 𝑠𝑖𝑛𝑐𝑒 𝑎𝑙𝑙 𝑆𝑝𝑟𝑖𝑛𝑔 𝐵𝑜𝑜𝑡 𝑡𝑒𝑠𝑡 𝑠𝑙𝑖𝑐𝑒 𝑎𝑛𝑛𝑜𝑡𝑎𝑡𝑖𝑜𝑛𝑠 𝑎𝑢𝑡𝑜𝑚𝑎𝑡𝑖𝑐𝑎𝑙𝑙𝑦 ℎ𝑎𝑛𝑑𝑙𝑒 𝑡ℎ𝑖𝑠 𝑝𝑟𝑜𝑐𝑒𝑠𝑠.
🅰️ What is the purpose of a JUnit Jupiter Extension?
The JUnit Jupiter extension model is a unified concept that enhances testing 🧪 functionality and allows for programmatic interception of test lifecycles.
It is a replacement 🔄️ for JUnit 4's Runner and Rule API.
Typically, extensions are implemented to address cross-cutting concerns that apply to multiple tests.
Numerous frameworks and testing libraries provide their own custom JUnit Jupiter extensions, such as
* 🍸 MockitoExtension for streamlined mock setup,
* 🐳 TestcontainersExtension (used with @Testcontainers) for managing Docker containers, and
* 🍃 SpringExtension for seamless integration with Spring.
🅱️ What is the purpose of the SpringExtension?
The SpringExtension serves several cross-cutting functionalities, as evidenced by its implementation in the source code.
It implements various interfaces🤹 , including BeforeAllCallback, AfterAllCallback, TestInstancePostProcessor, BeforeEachCallback, AfterEachCallback, BeforeTestExecutionCallback, AfterTestExecutionCallback, and ParameterResolver.
Its main responsibilities are as follows:
1. Managing the lifecycle 💗 of the Spring TestContext:
The SpringExtension ensures proper initialization, setup, and teardown of the Spring TestContext for test execution.
2. Supporting dependency injection 💉 for parameters:
It facilitates the injection of dependencies into test methods or constructors by resolving the required parameters.
3. Performing cleanup and housekeeping 🧹 tasks after the test:
The SpringExtension handles necessary cleanup 🧼 operations, ensuring that resources are properly released and any necessary cleanup tasks are performed.
The SpringExtension acts as a bridge 🌉 between JUnit Jupiter and the Spring Test framework.
In most cases, it delegates its responsibilities to the TestContextManager, which takes care of managing a single 1️⃣ TestContext.
⏺️ When is it necessary to register the SpringExtension?
In most scenarios, explicit registration of the SpringExtension is not ❌ required as it is already activated 👍 by default.
This activation occurs whenever we utilize a Spring Boot test annotation such as @WebMvcTest, @DataJpaTest, @JdbcTest, @DataMongoTest, @JsonTest, @RestClientTest, or @SpringBootTest.
However, there are certain limited situations where manual registration of the SpringExtension becomes necessary.
One example is when we create a custom test slice annotation, in which case we would need to explicitly register the SpringExtension to ensure its functionality is applied.
𝑇ℎ𝑒 𝑆𝑝𝑟𝑖𝑛𝑔𝐸𝑥𝑡𝑒𝑛𝑠𝑖𝑜𝑛 𝑖𝑚𝑝𝑙𝑒𝑚𝑒𝑛𝑡𝑠 𝑣𝑎𝑟𝑖𝑜𝑢𝑠 𝑐𝑎𝑙𝑙𝑏𝑎𝑐𝑘 𝑚𝑒𝑡ℎ𝑜𝑑𝑠 𝑜𝑓 𝑡ℎ𝑒 𝐽𝑈𝑛𝑖𝑡 𝐽𝑢𝑝𝑖𝑡𝑒𝑟 𝑒𝑥𝑡𝑒𝑛𝑠𝑖𝑜𝑛 𝑚𝑜𝑑𝑒𝑙, 𝑒𝑛𝑎𝑏𝑙𝑖𝑛𝑔 𝑠𝑚𝑜𝑜𝑡ℎ 𝑖𝑛𝑡𝑒𝑔𝑟𝑎𝑡𝑖𝑜𝑛 𝑏𝑒𝑡𝑤𝑒𝑒𝑛 𝐽𝑈𝑛𝑖𝑡 𝑎𝑛𝑑 𝑆𝑝𝑟𝑖𝑛𝑔.
𝐼𝑛 𝑡ℎ𝑒 𝑐𝑜𝑛𝑡𝑒𝑥𝑡 𝑜𝑓 𝑡𝑒𝑠𝑡𝑖𝑛𝑔 𝑆𝑝𝑟𝑖𝑛𝑔 𝐵𝑜𝑜𝑡 𝑎𝑝𝑝𝑙𝑖𝑐𝑎𝑡𝑖𝑜𝑛𝑠, 𝑡ℎ𝑒𝑟𝑒 𝑖𝑠 𝑢𝑠𝑢𝑎𝑙𝑙𝑦 𝑛𝑜 𝑛𝑒𝑒𝑑 𝑡𝑜 𝑚𝑎𝑛𝑢𝑎𝑙𝑙𝑦 𝑟𝑒𝑔𝑖𝑠𝑡𝑒𝑟 𝑡ℎ𝑖𝑠 𝑒𝑥𝑡𝑒𝑛𝑠𝑖𝑜𝑛 𝑏𝑒𝑐𝑎𝑢𝑠𝑒 𝑖𝑡 𝑖𝑠 𝑎𝑢𝑡𝑜𝑚𝑎𝑡𝑖𝑐𝑎𝑙𝑙𝑦 ℎ𝑎𝑛𝑑𝑙𝑒𝑑 𝑏𝑦 𝑡ℎ𝑒 𝑠𝑙𝑖𝑐𝑒𝑑 𝑐𝑜𝑛𝑡𝑒𝑥𝑡 𝑎𝑛𝑛𝑜𝑡𝑎𝑡𝑖𝑜𝑛𝑠 𝑠𝑢𝑐ℎ 𝑎𝑠 @𝑊𝑒𝑏𝑀𝑣𝑐𝑇𝑒𝑠𝑡.
𝐼𝑓 𝑦𝑜𝑢 𝑤𝑖𝑠ℎ 𝑡𝑜 𝑒𝑥𝑝𝑙𝑜𝑟𝑒 𝑡ℎ𝑖𝑠 𝑡𝑜𝑝𝑖𝑐 𝑓𝑢𝑟𝑡ℎ𝑒𝑟, 𝑟𝑒𝑓𝑒𝑟𝑟𝑖𝑛𝑔 𝑡𝑜 𝑡ℎ𝑒 𝑜𝑓𝑓𝑖𝑐𝑖𝑎𝑙 𝑑𝑜𝑐𝑢𝑚𝑒𝑛𝑡𝑎𝑡𝑖𝑜𝑛 𝑖𝑠 ℎ𝑖𝑔ℎ𝑙𝑦 𝑟𝑒𝑐𝑜𝑚𝑚𝑒𝑛𝑑𝑒𝑑 𝑎𝑠 𝑖𝑡 𝑝𝑟𝑜𝑣𝑖𝑑𝑒𝑠 𝑐𝑜𝑚𝑝𝑟𝑒ℎ𝑒𝑛𝑠𝑖𝑣𝑒 𝑖𝑛𝑓𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛 𝑜𝑛 𝑡ℎ𝑒 𝑠𝑢𝑏𝑗𝑒𝑐𝑡.