Difference between setUp and setUpBeforeClass

Question

When unit testing with JUnit  there are two similar methods  setUp   and setUpBeforeClass    What is the difference between these methods  Also  what is the difference between tearDown   and tearDownAfterClass     Here are the signatures    BeforeClass public static void setUpBeforeClass   throws Exception       AfterClass public static void tearDownAfterClass   throws Exception       Before public void setUp   throws Exception       After public void tearDown   throws Exception

User · Accepted Answer

The  BeforeClass and  AfterClass annotated methods will be run exactly once during your test run - at the very beginning and end of the test as a whole  before anything else is run   In fact  they re run before the test class is even constructed  which is why they must be declared static   The  Before and  After methods will be run before and after every test case  so will probably be run multiple times during a test run   So let s assume you had three tests in your class  the order of method calls would be   setUpBeforeClass       Test class first instance constructed and the following methods called on it      setUp       test1       tearDown       Test class second instance constructed and the following methods called on it      setUp       test2       tearDown       Test class third instance constructed and the following methods called on it      setUp       test3       tearDown    tearDownAfterClass

User · Answer

From the Javadoc      Sometimes several tests need to share computationally expensive setup  like logging into a database   While this can compromise the independence of tests  sometimes it is a necessary optimization  Annotating a public static void no-arg method with  BeforeClass causes it to be run once before any of the test methods in the class  The  BeforeClass methods of superclasses will be run before those the current class

User · Answer

setUpBeforeClass is run before any method execution right after the constructor  run only once   setUp is run before each method execution  tearDown is run after each method execution  tearDownAfterClass is run after all other method executions  is the last method to be executed   run only once deconstructor

User · Answer

Think of  BeforeClass  as a static initializer for your test case - use it for initializing static data - things that do not change across your test cases  You definitely want to be careful about static resources that are not thread safe   Finally  use the  AfterClass  annotated method to clean up any setup you did in the  BeforeClass  annotated method  unless their self destruction is good enough     Before   amp   After  are for unit test specific initialization  I typically use these methods to initialize   re-initialize the mocks of my dependencies   Obviously  this initialization is not specific to a unit test  but general to all unit tests

[java] Difference between setUp() and setUpBeforeClass()

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