How to use Interface ITest class of org.testng package

I assume you're using JUnit, and I assume by "instance variable (not static!)" you simply mean "test fixture class member" (or maybe you even mean "test case local variable").

Then the answer is "No - they will not share the same instance of the same variable". The JUnit runner will create different class instances for each test case and each test fixture. Each instance will run concurrently, but the class members will be separate and independent of each other.

Why not use an instance variable?

class YourClassTest {

  Sheet wbSheet;

  @BeforeTest public void readExcel(...) {
    wbSheet = wb.getSheet(sheetName);
  }

  @Test public void test() {
    //you can use wbSheet here
  }

}

The issue seems to be with the testng.xml. Make sure the first line of .xml file should be exactly as: <!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd">

the only issue here is "http" to be used instead of "https"

Here is the working solution for your problem. It uses JAVAX MAIL API and JAVA code. It does a lot more, so remove the code that u don't need.

  public GmailUtils(String username, String password, String server, EmailFolder 
    emailFolder) throws Exception {
    Properties props = System.getProperties();
    props.setProperty("mail.store.protocol", "imap");
    props.setProperty("mail.imaps.partialfetch", "false");
    props.put("mail.imap.ssl.enable", "true");
    props.put("mail.mime.base64.ignoreerrors", "true");

    Session session = Session.getDefaultInstance(props, null);
    Store store = session.getStore("imap");
    store.connect("imap.gmail.com", 993, "<your email>", "<your password>");

    Folder folder = store.getFolder(emailFolder.getText());
    folder.open(Folder.READ_WRITE);

    System.out.println("Total Messages:" + folder.getMessageCount());
    System.out.println("Unread Messages:" + folder.getUnreadMessageCount());

    messages = folder.getMessages();

    for (Message mail : messages) {
        if (!mail.isSet(Flags.Flag.SEEN)) {

            System.out.println("***************************************************");
            System.out.println("MESSAGE : \n");

            System.out.println("Subject: " + mail.getSubject());
            System.out.println("From: " + mail.getFrom()[0]);
            System.out.println("To: " + mail.getAllRecipients()[0]);
            System.out.println("Date: " + mail.getReceivedDate());
            System.out.println("Size: " + mail.getSize());
            System.out.println("Flags: " + mail.getFlags());
            System.out.println("ContentType: " + mail.getContentType());                
            System.out.println("Body: \n" + getEmailBody(mail));
            System.out.println("Has Attachments: " + hasAttachments(mail));

        }
    }
}


public boolean hasAttachments(Message email) throws Exception {

    // suppose 'message' is an object of type Message
    String contentType = email.getContentType();
    System.out.println(contentType);

    if (contentType.toLowerCase().contains("multipart/mixed")) {
        // this message must contain attachment
        Multipart multiPart = (Multipart) email.getContent();

        for (int i = 0; i < multiPart.getCount(); i++) {
            MimeBodyPart part = (MimeBodyPart) multiPart.getBodyPart(i);
            if (Part.ATTACHMENT.equalsIgnoreCase(part.getDisposition())) {
                System.out.println("Attached filename is:" + part.getFileName());

                MimeBodyPart mimeBodyPart = (MimeBodyPart) part;
                String fileName = mimeBodyPart.getFileName();

                String destFilePath = System.getProperty("user.dir") + "\\Resources\\";

                File fileToSave = new File(fileName);
                mimeBodyPart.saveFile(destFilePath + fileToSave);

                // download the pdf file in the resource folder to be read by PDFUTIL api.

                PDFUtil pdfUtil = new PDFUtil();
                String pdfContent = pdfUtil.getText(destFilePath + fileToSave);

                System.out.println("******---------------********");
                System.out.println("\n");
                System.out.println("Started reading the pdfContent of the attachment:==");


                System.out.println(pdfContent);

                System.out.println("\n");
                System.out.println("******---------------********");

                Path fileToDeletePath = Paths.get(destFilePath + fileToSave);
                Files.delete(fileToDeletePath);
            }
        }

        return true;
    }

    return false;
}

public String getEmailBody(Message email) throws IOException, MessagingException {

    String line, emailContentEncoded;
    StringBuffer bufferEmailContentEncoded = new StringBuffer();
    BufferedReader reader = new BufferedReader(new InputStreamReader(email.getInputStream()));
    while ((line = reader.readLine()) != null) {
        bufferEmailContentEncoded.append(line);
    }

    System.out.println("**************************************************");

    System.out.println(bufferEmailContentEncoded);

    System.out.println("**************************************************");

    emailContentEncoded = bufferEmailContentEncoded.toString();

    if (email.getContentType().toLowerCase().contains("multipart/related")) {

        emailContentEncoded = emailContentEncoded.substring(emailContentEncoded.indexOf("base64") + 6);
        emailContentEncoded = emailContentEncoded.substring(0, emailContentEncoded.indexOf("Content-Type") - 1);

        System.out.println(emailContentEncoded);

        String emailContentDecoded = new String(new Base64().decode(emailContentEncoded.toString().getBytes()));
        return emailContentDecoded;
    }

    return emailContentEncoded;

}

I think it's quite important feature for JUnit, if author of JUnit doesn't want the order feature, why?

I'm not sure there is a clean way to do this with JUnit, to my knowledge JUnit assumes that all tests can be performed in an arbitrary order. From the FAQ:

How do I use a test fixture?

(...) The ordering of test-method invocations is not guaranteed, so testOneItemCollection() might be executed before testEmptyCollection(). (...)

Why is it so? Well, I believe that making tests order dependent is a practice that the authors don't want to promote. Tests should be independent, they shouldn't be coupled and violating this will make things harder to maintain, will break the ability to run tests individually (obviously), etc.

That being said, if you really want to go in this direction, consider using TestNG since it supports running tests methods in any arbitrary order natively (and things like specifying that methods depends on groups of methods). Cedric Beust explains how to do this in order of execution of tests in testng.

Your test ckass needs to extend AbstractTestNGSpringContextTests. Or if your code is testing database acces another useful class to extend is AbstractTransactionalTestNGSpringContextTests.

From command line to gradle you can use system properties or project properties. It will be either:

./gradlew test -Denv=dev

or

./gradle test -Penv=dev

The properties above can be now read in a build.gradle, you need to pass them to tests as well, it must be done with system properties so:

test {
    systemProperty 'env', System.properties['env'] ?: 'dev'
}

for system properties from command line or:

test {
    systemProperty 'env', project.hasProperty('env') ? project.env : 'dev'
}

In test classes use just:

System.getProperty("env")

to get the value you need.

From the surefire-plugin documentation:

parallel (TestNG only) When you use the parallel attribute, TestNG will try to run all your test methods in separate threads, except for methods that depend on each other, which will be run in the same thread in order to respect their order of execution.

threadCount (TestNG only) The attribute thread-count allows you to specify how many threads should be allocated for this execution. Only makes sense to use in conjunction with parallel.

There is a section on running tests in parallel on the TestNG page of the plugin documentation. To do this your surefire plugin should be configured like this:

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <version>2.4.2</version>
  <configuration>
    <parallel>methods</parallel>
    <threadCount>10</threadCount>
  </configuration>
</plugin>

Question : The @test method will run for each row from the excel sheet when I use data provider?

Ans : Yes, it will run for each set of data. It depends on you how you read data from excel file.

Take this as an example :

@DataProvider(name = "test1")
public Object[][] createData1() {
 return new Object[][] {
   { "Cedric", new Integer(36) },
   { "Anne", new Integer(37)},
 };

@Test(dataProvider = "test1")
public void verifyData1(String n1, Integer n2) {
 System.out.println(n1 + " " + n2);
}

The verifyData1 method will be running two times irrespective of any set of data, irrespective of whether first one failed or not.

Q : What happens when one of the row failed to process?
Ans : Test case would be failed for that particular row , and execution will continue by reading the next set of data from excel.

Q. Does it run the rest of the rows after this failure?
Ans : Ideally it should , now again it depends whether you have @AfterMethod with you or not.

Q. Do I have to re-initiate the selenium webdriver and login method again when it fails?

Ans : No. It's better if you are initializing driver in @BeforeMethod , because before method would be running prior to each set of data which is generated by dataprovider.

Hope this will help.