AssertNull should be used or AssertNotNull

This is a pretty dumb question but my first time with unit testing so: lets say I have an object variable like obj and I want my unit test to Fail if this obj is Null. so for assertions, should I say AssertNull or AssertNotNull ? I get confused how they are named.

4 Answers

Use assertNotNull(obj). assert means must be.

The assertNotNull() method means "a passed parameter must not be null": if it is null then the test case fails.
The assertNull() method means "a passed parameter must be null": if it is not null then the test case fails.

String str1 = null; String str2 = "hello"; // Success. assertNotNull(str2); // Fail. assertNotNull(str1); // Success. assertNull(str1); // Fail. assertNull(str2); 

assertNotNull asserts that the object is not null. If it is null the test fails, so you want that.

I just want to add that if you want to write special text if It null than you make it like that

 Assert.assertNotNull("The object you enter return null", str1)