assertSame and assertNotSame in JUnit - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does assertSame check in JUnit?

assertSame checks if two references point to the exact same object in memory.

beginner

What is the difference between assertSame and assertEquals?

assertSame checks if two references are identical (same object), while assertEquals checks if two objects are logically equal (same content).

beginner

What does assertNotSame verify?

assertNotSame verifies that two references do NOT point to the same object in memory.

beginner

Give a simple example of using assertSame in a test.

Example:<br>

String a = "hello";<br>String b = a;<br>assertSame(a, b); // Passes because both refer to the same object

intermediate

Why might assertSame fail even if two objects look equal?

Because assertSame checks object identity, not content. Two different objects with the same content will fail assertSame.

What does assertSame(obj1, obj2) verify in JUnit?

A obj1 and obj2 are the exact same object

B obj1 and obj2 have the same content

C obj1 is not null

D obj1 and obj2 are different objects

assertSame checks if both references point to the same object in memory.

Which assertion would you use to check that two variables do NOT refer to the same object?

A assertSame

B assertEquals

C assertNotSame

D assertNull

assertNotSame verifies that two references are not the same object.

If assertEquals(obj1, obj2) passes but assertSame(obj1, obj2) fails, what does it mean?

A obj1 and obj2 are the same object

B Test is invalid

C obj1 is null

D obj1 and obj2 have equal content but are different objects

assertEquals checks content equality; assertSame checks object identity.

Which of these is a correct use of assertNotSame?

A assertNotSame(new String("a"), new String("a"))

B assertNotSame("a", "a")

C assertNotSame(null, null)

D assertNotSame(obj, obj)

Two different String objects with same content are not the same object, so assertNotSame passes.

What will happen if assertSame(obj1, obj2) is used and obj1 is null but obj2 is not?

A Test passes

B Test fails

C Throws exception

D Test is skipped

assertSame fails if references are not the same, including if one is null and the other is not.

Explain in your own words the difference between assertSame and assertEquals.

Think about whether the test checks if two things are literally the same object or just look the same.

Describe a situation where using assertNotSame is important in testing.

Consider cases where sharing the same object could cause bugs.