Populating Spring @Value during Unit Test

Injecting Static Values using ReflectionTestUtils

Without loading the full Spring context, you can set property values straight in your test:

@BeforeEach
void setUp() {
    // Trust me, it's not dark magic, just ReflectionTestUtils
    ReflectionTestUtils.setField(myBean, "myProperty", "desiredValue");
}
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myBean is your test instance, myProperty is the annotation field marked with @Value, and "desiredValue" is the string value you want to populate.

Alternatives to @Value Injection

@Value may not always be your best bet. Consider these alternatives:

• Constructor Injection: Directly passing values, which brings clarity.
• Setter Injection: Allows logic-based property population.
• @ConfigurationProperties: For a type-safe approach and complex configurations.

Slimming Down your Tests

In unit testing, speed and simplicity matter. Avoid loading the full Spring context wherever possible:

• Mock Dependencies: Use Mockito for mocking beans interacted by your test unit. Keeps your test lean and mean.
• Plain Jane Java Objects: ReflectionTestUtils works not only with Spring beans but any regular Java object. Your objects don't have to be all springy!

An Ounce of Prevention...

Keep your unit tests reliable and resilient to external changes:

• Avoid External Properties Files: Keep your tests self-contained. Say no to surprises!
• Dedicated Test Configurations: Use @Configuration classes to define test-only beans. Keep your testing scenarios undramatic.