JUnit Testing Exceptions

Question

I m really new to java    I m running some JUnit tests on a constructor  The constructor is such that if it is given a null or an empty string for one of its parameters  it s supposed to throw an exception    When I test this constructor in JUnit with a null or an empty string parameter  I get a red bar  even though I m almost 100  sure that the constructor method does indeed throw an exception when such parameters are passed in to it    Shouldn t there be a green bar in JUnit if the method throws an exception the way it is supposed to  Or is it that when you are supposed to get a red bar when the exception throwing works the way it is supposed to

User · Answer

Though  Test expected   MyException class  and the ExpectedException rule are very good choices  there are some instances where the JUnit3-style exception catching is still the best way to go    Test public void yourTest       try       systemUnderTest doStuff        fail  MyException expected         catch  MyException expected            Though the ExpectedException rule lets you write matchers about        exceptions  it is sometimes useful to inspect the object directly       assertEquals 1301  expected getMyErrorCode               In both  Test expected      and ExpectedException code  the      exception-throwing line will be the last executed line  because Java will      still traverse the call stack until it reaches a try block--which will be      inside the JUnit framework in those cases  The only way to prevent this      behavior is to use your own try block        This is especially useful to test the state of the system after the      exception is caught     assertTrue systemUnderTest isInErrorState         Another library that claims to help here is catch-exception  however  as of May 2014  the project appears to be in maintenance mode  obsoleted by Java 8   and much like Mockito catch-exception can only manipulate non-final methods

User · Answer

are you sure you told it to expect the exception   for newer junit     4 7   you can use something like  from here    Rule public ExpectedException exception   ExpectedException none      Test public void testRodneCisloRok        exception expect IllegalArgumentException class       exception expectMessage  error1        new RodneCislo  891415  dopocitej  891415         and for older junit  this    Test expected   ArithmeticException class    public void divisionWithException         int i   1 0

User · Answer

If your constructor is similar to this one   public Example String example        if  example    null            throw new NullPointerException                do fun things with valid example here     Then  when you run this JUnit test you will get a green bar    Test expected   NullPointerException class  public void constructorShouldThrowNullPointerException         Example example   new Example null

User · Answer

An adventage of use ExpectedException Rule  version 4 7  is that you can test exception message and not only the expected exception   And using Matchers  you can test the part of message you are interested   exception expectMessage containsString  income  -1000 0

User · Answer

Test expected   Exception class      Tells Junit that exception is the expected result so test will be passed  marked as green  when exception is thrown      For   Test   Junit will consider test as failed if exception is thrown  provided it s an unchecked exception  If the exception is checked it won t compile and you will need to use other methods  This link might help

[java] JUnit Testing Exceptions

Examples related to java

Examples related to junit