AssertSameObject

AssertSameObject is a unit testing assertion that verifies two references point to the exact same object instance. It tests identity rather than structural or value equality, meaning it passes only when both operands reference the same underlying object.

Semantics and behavior

The assertion uses reference or pointer identity. If both arguments refer to the same object, the test passes; if they refer to different objects, even with identical content, the test fails. In languages with null references, the assertion typically passes only when both sides are the same non-null object, and may fail if one side is null while the other is not.

Common usage

AssertSameObject is used to confirm scenarios where object reuse is required or expected, such as verifying a singleton, shared cache, or memoized instance. It helps catch errors where code creates new objects unnecessarily or where state is not being shared as intended.

Signature and behavior variation

The exact syntax and exception type vary by library or language, but the core idea remains: the function raises an assertion failure if the two operands are not the same object. Some frameworks expose similar checks under names like assertSame, AreSame, or assertIs, but the behavior is the same: identity comparison rather than deep equality.

In practice

When debugging, ensure you are testing identity rather than equality of contents. Be mindful of language-specific details on how references and nulls are handled. While not every framework provides assertSameObject by this exact name, the concept is widely available across testing libraries.