JUnit for both try and catch block coverage

Question

I am trying to write a JUnit for below code but I am not getting any idea how to cover the code which is written in catch block statement. Please can any one write a sample JUnit for below code.

Here I don't want to cover any exception, but want to cover the lines of code written in the catch block using Mockito.

public Product getProductLookUpData() { Product product = null; try{ // Try to get value from cacheable method product = productCacheDao.getProductLookUpData(); .....//statements } catch (Exception ex) { // getting value from db product = productDao.getIpacMetricCodeLookUpData(); ....//statements } return product; }

If you want to cover the code in the catch block, your test needs to cause an exception to be thrown in the try block. — khelwood
– khelwood, Commented Feb 28, 2017 at 12:06
You will have to setup your test such that it will throw an exception. — Abubakkar
– Abubakkar, Commented Feb 28, 2017 at 12:06
Yes i have tried that, but code is not entering into getProductLookUpData() catch block it is directly throwing exception and getting assertion failed. — John
– John, Commented Feb 28, 2017 at 12:09
Possible duplicate of How to cover block catch by JUnit with NoSuchAlgorithmException and KeyStoreException — Tom
– Tom, Commented Feb 28, 2017 at 12:36

esin88 · Accepted Answer · 2017-02-28 12:49:15Z

You can mock both productCacheDao and productDao and check how many times those methods were invoked in your test cases. And you can simulate exception throwing with those mock objects, like this:

when(mockObject.method(any())).thenThrow(new IllegalStateException());

So, for your case I would do something like this:

import org.junit.Assert; import org.junit.Before; import org.junit.Test; import static org.mockito.Mockito.*; public class ProductTest { private static final Product CACHED_PRODUCT = new Product("some parameters for cached product"); private static final Product DB_PRODUCT = new Product("some parameters for DB product"); private ProductService service; private ProductDao productDaoMock; private ProductCacheDao productCacheDaoMock; @Before public void setup() { service = new ProductService(); productDaoMock = mock(ProdoctDao.class); service.setProductDao(productDaoMock); productCacheDaoMock = mock(ProdoctCacheDao.class); service.setProductCacheDao(productCacheDaoMock); } @Test public void testCache() { when(productCacheDaoMock.getProductLookUpData(any())).thenReturn(CACHED_PRODUCT); final Product product = service.getProductLookUpData(); Assert.assertEquals(CACHED_PRODUCT, product); verify(productCacheDaoMock, times(1)).getProductLookUpData(any()); verify(productDaoMock, never()).getIpacMetricCodeLookUpData(any()); } @Test public void testDB() { when(productCacheDaoMock.getProductLookUpData(any())).thenThrow(new IllegalStateException()); when(productDaoMock.getIpacMetricCodeLookUpData(any())).thenReturn(DB_PRODUCT); final Product product = service.getProductLookUpData(); Assert.assertEquals(DB_PRODUCT, product); verify(productCacheDaoMock, times(1)).getProductLookUpData(any()); verify(productDaoMock, times(1)).getIpacMetricCodeLookUpData(any()); } }

If i mock and expect the exception as the you gave the link will it cover the code of the catch block.
You can mock both those ojects: productCacheDao and productDao. Then, you should have 2 test cases: one for using productCacheDao and one for productCacheDao throwing exception and using productDao. In those cases you can check, how many times your methods were invoked with verify method. Watch this question for example: stackoverflow.com/questions/27787487/…
@Pavan added mockito example. In the first case you check that your cache method was invoked once, and your DB method was never invoked. In the second case your cache method throws exception, and you check that your DB method was invoked once.

Adam · Accepted Answer · 2017-02-28 12:18:52Z

Mockito, or another mocking framework can be used. You will need two test cases - with and without the exception being thrown. You can mock your DAOs to return a known object so you verify your service is exhibiting the correct behaviour.

I've written a full example below.

public class MocksExample { private ProductService service; @Mock private ProductDao productDao; @Mock private ProductCacheDao productCacheDao; @Mock private Product product; @Before public void setup() { MockitoAnnotations.initMocks(this); service = new ProductService(); service.setProductCacheDao(productCacheDao); service.setProductDao(productDao); } @Test public void serviceReturnsProduct() { when(productCacheDao.getProductLookUpData()).thenReturn(product); assertThat(service.getProductLookUpData(), is(product)); } @Test public void ipacProductReturnedWhenDaoThrowsException() { when(productDao.getIpacMetricCodeLookUpData()).thenReturn(product); when(productCacheDao.getProductLookUpData()).thenThrow(new IllegalStateException("foo")); assertThat(service.getProductLookUpData(), is(product)); } }

thopaw · Accepted Answer · 2017-02-28 12:12:29Z

You can use Mocking frameworks like Mockito

In your JUnit Test you can do something like

public class YourTest { private ProductcacheDao productCacheDaoMock; @Before public void setup() throws Exception { productCacheDaoMock = Mockito.mock(ProductcacheDao.class); } @org.junit.Test public void test() { // Given Mockito.when(productCacheDaoMock.getProductLookUpData()).thenThrow(new RuntimeException()); // When // do your stuff productCacheDaoMock.getProductLookUpData(); // Then // ... } }

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