Checks that constructors and assignment operators marked as = default are not actually deleted by the compiler.

class Example {
public:
// This constructor is deleted because I is missing a default value.
Example() = default;
// This is fine.
Example(const Example& Other) = default;
// This operator is deleted because I cannot be assigned (it is const).
Example& operator=(const Example& Other) = default;

private:
const int I;
};