TestTraits.java

public interface TestTraits {
    String EMPLOYEE_ID = "1";
    Long EMPLOYEE_ID_LONG = 1L;

    default EmployeeRpy getEmployee(){
        EmployeeRpy objEmpRpy = new EmployeeRpy();
        objEmpRpy.setEmpName("Mugil");
        objEmpRpy.setEmpAge("34");
        return objEmpRpy;

     default EmployeeDetailsResource createMockedEmployeeDetails() 
          throws IOException(){
       EmployeeDetailsResource objEmployeeDetailsResource = 
              new Gson.fromJson(getReader("json-data/EmployeeDetails.json"), EmployeeDetails.class);    
       return objEmployeeDetailsResource; 
     } 

     default Reader getReader(String filePath) throws IOException{
       return new FileReader(new ClassPathResource(filePath).getFile());  
     }
}

EmployeeDetails.json

  {
     "empID" : "101",
     "empName" : "Mugilvannan",
     "empAge" : "30"
  } 

EmployeeMgmtTest.java

 @ExtendWith({MockitoExtension.class})
 class EmployeeMgmtTest implements TestTraits{
    .
    . 
    Code for Testing Goes Here
    .
    .
 }
  1. @BeforeAll, @AfterAll – Runs Before and After Class and should be static
  2. @DisplayName – Displays description about the Test Method
  3. @Disabled – @Ignore in Junit 4. Disables the Test Method
  4. @Nested – Helps in grouping of similar test methods together
  5. @ParameterizedTest – Supplying more than one input for same method in row using array
  6. @ValueSource – Provides multiple paramters to same test method for ParameterizedTest
  7. @CsvSource – Provides multiple paramters to same test method for ParameterizedTest in Key Value Pair. Key is Input and Value is expected Output

AccountUtils.java

import java.io.IOException;

public class AccountUtils {

    public boolean validateAccountId(String acctNo) throws IOException {
        if (getAccountIDLength(acctNo)) {
            return true;
        } else {
            throw new IOException("Account ID is Invalid");
        }
    }

    public boolean getAccountIDLength(String acctNo)
    {
        if(acctNo.length() < 5) return false;
        if(acctNo.length() > 10) return false;
        if(!acctNo.contains("-")) return false;

        return true;
    }

    public  String getFormattedAccID(String accountNo){
        return accountNo.toUpperCase();
    }

    public String[] getBankDetails(String accountNo){
        String[] arrAccountDetails = accountNo.split("-");
        return arrAccountDetails;
    }
}

AccountUtilsTest.java

import org.junit.jupiter.api.*;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.CsvSource;
import org.junit.jupiter.params.provider.ValueSource;

import java.io.IOException;

import static org.junit.jupiter.api.Assertions.fail;

public class AccountUtilsTest {

    AccountUtils systemUnderTest = new AccountUtils();

    @BeforeAll
    static void init(){
        System.out.println("Initilize connection to Database");
    }

    @AfterAll
    static void destroy(){
        System.out.println("Deallocate connection to Database");
    }

    @Test
    @DisplayName("AccountID Length Validation Success")
    void test_getAccountIDLength_Success(){
        boolean expectedOutput = true;
        boolean actualOutput = systemUnderTest.getAccountIDLength("SBI-104526");

        Assertions.assertEquals(expectedOutput, actualOutput);
        Assertions.assertTrue(actualOutput);
    }

    @Test
    @Disabled
    void test_validateAccountId_Success() throws IOException {
        Assertions.assertTrue(systemUnderTest.validateAccountId("SBI-104526"));
    }

    @Test
    @DisplayName("AccountID is Invalid ")
    void test_validateAccountId_Exception(){
        Assertions.assertThrows(IOException.class, ()->{
            systemUnderTest.validateAccountId("");
        });
    }

    @Test
    @DisplayName("Account Bank Details Validation")
    void test_AccountIDForBankName_Success(){
        String[] expectedOutput = new String[]{"SBI", "104526"};
        String[] actualOutput = systemUnderTest.getBankDetails("SBI-104526");

        Assertions.assertArrayEquals(expectedOutput, actualOutput);
    }

    @Nested
    class checkValidAccountId
    {
        @ParameterizedTest
        @ValueSource(strings={"SBI", "SBI-123456789", " ", ""})
        @DisplayName("Parameterized Test AccountID Length Validation Failiure")
        void test_getAccountIDLength_Failiure(String accountId){
            Assertions.assertFalse(systemUnderTest.getAccountIDLength(accountId));
        }

        @ParameterizedTest(name="AccountID {0} formatted to {1}")
        @CsvSource(value={"sbi-123456, SBI-123456", "cbi-123456, CBI-123456"})
        @DisplayName("AccountID Format Validation")
        void getFormattedAccID_Success(String inputString, String expectedOutput){
            Assertions.assertEquals(expectedOutput, systemUnderTest.getFormattedAccID(inputString));
        }
    }
}
Junit 5 = Platform + Jupiter + Vintage 
  1. Platform = Engine + Runner + Launcher
  2. All the Class files needed for Coding Test Cases
  3. Provides Support for Junit3 and 4

Adding Dependency in pom.xml for Junit 5

JUnit 5 Platform
includes junit-jupiter-api + junit-platform-engine

<dependencies>
    [...]
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter-engine</artifactId>
        <version>5.4.0</version>
        <scope>test</scope>
    </dependency>
    [...]
</dependencies>

If you want to write and execute JUnit 3 or 4 tests via the JUnit Platform add the Vintage Engine to the dependencies

<dependencies>
    [...]
    <dependency>
        <groupId>org.junit.vintage</groupId>
        <artifactId>junit-vintage-engine</artifactId>
        <version>5.4.0</version>
        <scope>test</scope>
    </dependency>
    [...]
</dependencies>