Every @Test has meaningful name ('validateUserCannotLoginWithWrongCredentialsTest' vs 'badLoginTest')

Add JavaDoc for every test with meaningful descriptions and incoming parameters

Each assert besides actual and expected result should also have 'message, to be printed in case if the test fails (Assert.assertEquals("How are you, subscriber subscriber?", source.getText(), "OOPS! The test failed because of ...");

There's no Thread.Sleep in your code. If there're some of them, replace them with explicit or implicit wait, depending on the case

Each test method has logging added (log.info, log.debug, log.error, etc.) and not a System.out.println

If you verify few results in 1 test, use rather SoftAssert() than general Assert() for each of them

Whenever possible, use Fluent / Chain of Invocations for Page Object (PO) methods instead of invoking PO instance every time ( https://snag.gy/FJlkcR.jpg )

Make sure, the screenshot will be taken when your test fails

Every @Test has meaningful name ('validateUserCannotLoginWithWrongCredentialsTest' vs 'badLoginTest')

There's no Thread.Sleep in your code. If there're some of them, replace them with explicit or implicit wait, depending on the case

Each test method has logging added (log.info, log.debug, log.error, etc.) and not a System.out.println