JUnit tests should include at least one assertion. Using a message for each assertion makes the reason for failure more clear and makes the test easier to maintain and debug.
Example:
public class Foo extends TestCase {
public void testSomething() {
Bar b = findBar();
// This is better than having a NullPointerException
// assertNotNull("bar not found", b);
b.work();
}
}
Source: http://pmd.sourceforge.net/pmd-4.3.0/rules/junit.html
