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javaunit-testingassertj

AssertJ combine exception catching and return type assertions

I have a method which catches an IOException while trying to process a JSON file and if this exception occurs false is being returned. Something like:

public boolean method(){
 try{
  // process json file
   return true;
 } catch IOException {
   // write stuff into db
   return false;
 }
}

The catch block writes exception message to the database. So given a method with a boolean return type and exception handling how can I combine both in my unit test to assert the instance of the exception/its message and method's return value? I am aware of

Assertions.assertThatThrownBy(() -> objectUnderTest.method()).isInstanceOf(IOException.class)

The above statement results in: java.lang.AssertionError: Expecting code to raise a throwable.

and

Assertions.assertThat(objectUnderTest.method()).isFalse() // works well
Solution

  • As the exception is caught in the method, AssertJ has no chance to see it, hence the assertion error you already experienced.

    Assuming you are in a unit test with a mock of the DB writer, you might intercept that call of the mock and assert the invocation parameter(s).

    If you aren't in a unit test, you should read back from the DB and assert its content.