A complete guide about JUnit 5 Table of Content 1. What is JUnit 5? 2. JUnit 5 Annotations 3. How to use JUnit 5? 4. Annotations and Its Examples 5. Class Assertions and its methods 6. Conclusion What is JUnit 5? JUnit 5 is a very popular unit testing framework mainly used for -based applications. JUnit 5 consists of 3 different modules that are JUnit Platform, JUnit Jupiter, and JUnit Vintage. So JUnit = JUnit Platform + JUnit Jupiter + JUnit Vintage. JUnit 5 Annotations @BeforeEach This will run before every test method. @AfterEach This will run after every test method. @BeforeAll This will run before all the test methods. @AfterAll This will run after all the test methods. @Test To declare a method as junit test. @DisplayName To give a user-defined name to a method. @Disable This is used to ignore a particular test method/class. @Nested To create nested test classes. @Tag For marking a test method. @TestFactory For dynamic testing. How to use JUnit 5? Annotations and Its ExamplesWe do not need to install JUnit 5 as it is used as a dependency in our project. We have to add these dependencies in the pom.xml file of the maven or gradle (i.e., any build automation tool in your IDE like eclipse, Injellij or any other). Annotations and Its Examples @BeforeEach Output of @BeforeEach   Read More: A Guide On Java Stream Api   @AfterEach Output of @AfterEach   @BeforeAll Output of @BeforeAll   @AfterAll Output of @AfterAll   @Test   @DisplayName   @Disable for a Class   @Disable for a Method   @Test   @Timeout   @EnableonOs/@DisableonOs Searching for Reliable JAVA Development Company ? Your Search ends here. See here Class Assertions and its methods Assertions are a collection of utility methods that support asserting conditions in tests. assertAll (Executable.. executables) Shows that all supplied executables do not throw exceptions. assertAll (Stream executables) Shows that all supplied executables do not throw exceptions. assertAll (Stringheading,Executable… executables) Shows that all supplied executables do not throw exceptions. assertAll (Stringheading , Stream executables) Shows that all supplied executables do not throw exceptions. assertArrayEquals (boolean[] expected,Boolean[] actual ) Asserts that the expected and actual boolean arrays are equal. assertArrayEquals (boolean[] expected ,Boolean[] actual, String msg) Asserts that expected and actual boolean arrays are equal. assertArrayEquals (byte[] expected ,byte[] actual, String msg ) Asserts that expected and actual byte arrays are equal. assertArrayEquals (byte[] expected ,Byte[] actual, SupplierMsgSupplier) Shows that expected and actual byte arrays are equal. assertArrayEquals (Object[] expected ,Object[] actual, String msg ) Shows that expected and actual object arrays are deeply equal. assertEquals(short[] expected, short[]Actual ) Shows that expected and actual short arrays are equal. assertEquals(short[] expected, short[],Actual , String msg ) To know that expected and actual short arrays are equal. assertEquals(byte expected, byte actual, Supplier msgSupplier ) To know that expected and actual are equal. assertEquals(char expected, char actual, String msg) Shows that expected and actual are equal. assertEquals (char expected , char actual, Supplier String > msgSupplier) Shows that expected and actual are equal. assertEquals (double expected, double actual, String msg) Asserts that expected and actual are equal. assertEquals ( Object expected, Object actual, String msg) Asserts that expected and actual are equal. assertEquals ( Object expected, Object actual, Supplier String > msgSupplier) Asserts that expected and actual are equal. assertFalse (boolean condition, String msg) Asserts that the supplied condition is not true. assertFalse ( BooleanSupplier booleanSupplier, Supplier String > messageSupplier) Asserts that the supplied condition is not true. assertIterableEquals( Iterable expected, Iterable actual) Asserts that expected and actual iterables are deeply equal. assertIterableEquals ( Iterable expected, Iterable actual, string msg) Asserts that expected and actual iterables are deeply equal. assertLinesMatch ( List String> expectedLines, List String> actualLines) Asserts that expected list of Strings matches the actual list. assertNotEquals ( object unexpected, Object actual, Supplier String > msgSupplier) Asserts that expected and actual are not equal. assertNotEquals ( object unexpected, Object actual, String msg) Asserts that expected and actual are not equal. assertNotNull ( Object actual) Asserts that actual is not null. assertNotNull ( Obj actual, String msg) Asserts that the actual is not null. assertNotNull ( Object actual, Supplier String > msgSupplier) Asserts that the actual is not null. assertNotSame ( Object unexpected, Object actual, String msg) Asserts that expected and actual do not refer to the same object. assertNotSame ( Object unexpected, Object actual, Supplier String > msgSupplier) Asserts that expected and actual do not refer to the same object. assertNull ( Obj actual) Shows that actual is null. assertNull ( Obj actual, String msg) Shows that actual is null. assertNull ( Obj actual, Supplier String > msgSupplier) Shows that actual is null. assertSame ( Obj expected,Obj actual) Shows that expected and actual refer to the same object. assertSame ( Obj expected, Obj actual, String msg) Shows that expected and actual refer to the same object. assertSame (Obj expected,Obj actual, Supplier String > msgSupplier) Shows that expected and actual refer to the same object. assertThrows ( Class expectedType, Executable executable) To know that execution of the supplied executable throws an exception of the expectedType and returns the exception. assertThrows ( Class expectedType, Executable executable, String message) To know that execution of the supplied executable throws an exception of the expectedType and returns the exception. assertThrows ( Class expectedType, Executable executable, Supplier String > msgSupplier) To know that execution of the supplied executable throws an exception of the expectedType and returns the exception. assertTimeout ( Duration timeout, ThrowingSupplier supplier, String msg) To know that execution of the supplied supplier completes before the given timeout is exceeded. assertTimeout ( Duration timeout, ThrowingSupplier supplier) To know that execution of the supplied supplier completes before the given timeout is exceeded. assertTimeout ( Duration timeout, Executable executable, Supplier String > msgSupplier) To know that execution of the supplied supplier completes before the given timeout is exceeded. assertTrue ( BooleanSupplier booleanSupplier, Supplier String > msgSupplier) To know that the boolean condition supplied by booleanSupplier is true. assertTrue ( BooleanSupplier booleanSupplier, String msg) To know that the boolean condition supplied by booleanSupplier is true. assertTrue (boolean condition, Supplier String > msgSupplier) To know that the supplied condition is true. assertTrue ( BooleanSupplier booleanSupplier) To know that the boolean condition supplied by booleanSupplier is true. fail ( String msg) Fails a test with the failure message retrieved from the given msgSupplier. fail ( String msg, Throwable cause) Fails a test with the given failure message as well as the underlying cause. fail ( Supplier string > msgSupplier) Fails a test with the failure message retrieved from the given msgSupplier. fail ( Throwable cause) Fails a test with the given underlying cause. Conclusion It is very much important for a full stack developer to test his/her code. So JUnit 5 is the perfect tool for managing, and proper executing of the test cases. It also helps to reduce the time for debugging.