How to write junit test cases for IOException

Question

I want to check the IOException class in JUNIT testing. Here is my code:

public void loadProperties(String path) throws IOException {
  InputStream in = this.getClass().getResourceAsStream(path);
  Properties properties = new Properties();
  properties.load(in);
  this.foo = properties.getProperty("foo");
  this.foo1 = properties.getProperty("foo1");
}

when I try to give false properties file path it gives NullPointerException. I want to get IOException and Junit test for it. Thank you very much for your help.

Answer 1

Try this

public TestSomeClass
{
    private SomeClass classToTest; // The type is the type that you are unit testing.

    @Rule
    public ExpectedException expectedException = ExpectedException.none();
    // This sets the rule to expect no exception by default.  change it in
    // test methods where you expect an exception (see the @Test below).

    @Test
    public void testxyz()
    {
        expectedException.expect(IOException.class);
        classToTest.loadProperties("blammy");
    }

    @Before
    public void preTestSetup()
    {
        classToTest = new SomeClass(); // initialize the classToTest
                                       // variable before each test.
    }
}

Some reading: jUnit 4 Rule - scroll down to the "ExpectedException Rules" section.