Q:
JUnit Test case for exception throwing
I'm new to Java and JUnit. I have a class that contains a switch-case block. I want to test for all the cases possible error or failure exceptions are thrown.
public void testExceptions() {
// Call the method that throws exceptions
ClassUnderTest.test();
// Check the expected exceptions are thrown
List exceptionMessages = TestUtil.checkExceptionThrown(ClassUnderTest.class);
assertEquals(true, exceptionMessages.size() > 0);
}
ClassUnderTest::test:
@Override
public String test() {
int status = Class1.status;
switch(status){
case 1: {
return "this is the exception";
break;
}
case 2: {
return "this is another exception";
break;
}
case 3: {
return "yet another exception";
break;
}
case 4: {
return "another one";
break;
}
case 5: {
return "this is an exception";
break;
}
}
throw new Class1Exception();
}
The expected is that in every case an exception is thrown and hence an exception is thrown. The assertion fails when there is no exception. What am I missing here?
I tried it like below and it doesn't work. It still passes for me although I have tested for the expected exception being thrown.
//I have used assertions
@Test (expected=Class1Exception.class)
public void test1() {
int status = Class1.status;
switch(status){
case 1: {
return "this is the exception";
break;
}
case 2: {
return "this is another exception";
break;
}
case 3: {
return "yet another exception";
break;
}
case 4: {
return "another one";
break;
}
case 5: {
return "this is an exception";
break;
}
}
}
Is the @Test (expected=Class1Exception.class) correct? I thought it is only going to check if the Expected exception is thrown or not. It checks if it's the same class. I want to make sure that for all the exceptions an exception is thrown. What am I missing here? How can I test this?
I also tried using ExpectedException:
@Test(expected=Class1Exception.class)
public void test1() throws Class1Exception {
int status = Class1.status;
switch(status){
case 1: {
return "this is the exception";
break;
}
case 2: {
return "this is another exception";
break;
}
case 3: {
return "yet another exception";
break;
}
case 4: {
return "another one";
break;
}
case 5: {
return "this is an exception";
break;
}
}
}
But it still fails. I wonder why it doesn't work. Can anyone guide me about how I can write JUnit test case for this?
A:
Is the @Test (expected=Class1Exception.class) correct?
Yes it's correct. You need to ensure the test method contains throws clause and that method will be wrapped into try/catch block in the method under test.
I want to make sure that for all the exceptions an exception is thrown.
I would use @Rule with @Test(expected=...) for this case. There is one caveat in your case - you have no control which is thrown exception. The easiest way to get this work - use Exception:
public class MyTest {
@Rule
public TestRule exceptionHandler = new TestRule() {
@Override
public Statement apply(final Statement base,final Description description) {
return new Statement() {
@Override
public void evaluate() throws Throwable {
try {
base.evaluate();
} catch (Exception e) {
throw new AssertionError("Expected exception", e);
}
}
};
}
};
@Test
public void test1() throws Class1Exception {
int status = Class1.status;
switch (status) {
case 1: {
return "this is the exception";
break;
}
case 2: {
return "this is another exception";
break;
}
case 3: {
return "yet another exception";
break;
}
case 4: {
return "another one";
break;
}
case 5: {
return "this is an exception";
break;
}
}
}
}
UPDATED:
I created a sample code that covers your case:
@Test(expected=IllegalArgumentException.class)
public void testSwithCase() throws Exception {
String test = null;
switch (test) {
case "1":
throw new IllegalArgumentException("this is the exception");
case "2":
throw new IllegalArgumentException("this is another exception");
case "3":
throw new IllegalArgumentException("yet another exception");
case "4":
throw new IllegalArgumentException("another one");
case "5":
throw new IllegalArgumentException("this is an exception");
}
}
public static class MyClass {
public void method() {
String test = null;
switch (test) {
case "1":
throw new IllegalArgumentException("this is the exception");
case "2":
throw new IllegalArgumentException("this is another exception");
case "3":
throw new IllegalArgumentException("yet another exception");
case "4":
throw new IllegalArgumentException("another one");
case "5":
throw new IllegalArgumentException("this is an exception");
}
}
public static void test(String param) throws IllegalArgumentException {
switch (param) {
case "1":
method();
break;
case "2":
method();
break;
case "3":
method();
break;
case "4":
method();
break;
case "5":
method();
break;
}
}
}
import org.junit.Test;
import org.junit.Assert;
import static org.junit.Assert.*;
public class TestClass {
@Test
public void test() {
String test = "1";
Assert.assertNotNull(test);
Assert.assertTrue(test == "1" || test == null);
try {
MyClass.test(test);
} catch (IllegalArgumentException e) {
Assert.assertEquals(true, true);
Assert.assertEquals(e.getMessage(), test);
}
}
@Test
public void testShouldPass() throws Exception {
String test = "1";
// no throw
try {
MyClass.test(test);
} catch (IllegalArgumentException e) {
Assert.assertEquals(true, true);
Assert.assertEquals(e.
