@BeforeClass

Internal

• JUnit

Overview

The annotation must be attached to a static method.

@BeforeClass and Class Hierarchies

If two methods with different names are annotated with @BeforeClass in a test class hierarchy, as shown below:

TestBase.java
  │  @BeforeClass
  │  public static void testBaseOneTimeSetup() {
  │     ...
  │  }
  │
  └── SomeTest.java
        @BeforeClass
        public static void someTestOneTimeSetup() {
          ...
        }

then both methods are executed only once, in this order: first the parent class method (testBaseOneTimeSetup()), then the subclass method (someTestOneTimeSetup()). The rule holds true in a multi-layer hierarchy.

However, if both methods have the same name, an override of sorts takes place and only the method belonging to the subclass is executed:

TestBase.java
  │  @BeforeClass
  │  public static void oneTimeClassSetup() {
  │     ...
  │  }
  │
  └── SomeTest.java
        @BeforeClass
        public static void oneTimeClassSetup() {
          ...
        }

Only SomeTest.oneTimeClassSetup() is executed, so if you need the logic executed in superclass, it must be invoked explicitly with: <syntaxhighlight lang='java'> class SomeTest {

 @BeforeClass
 public static void oneTimeClassSetup() {
    TestBase.oneTimeClassSetup();
 }

} <syntaxhighlight lang='java'>

In conclusion, if class-level one-time initialization is needed for each level of a class hierarchy, the best solution is to name @BeforeClass methods differently for each class. This way, all methods are executed in order, starting from the root of the hierarchy and continuing towards the bottom.