/tests/Unit/OptionTest.php
 [x] `->value` → retrieves the value for Some
 [x] `->value` → throws an exception for None
 [x] `->isNone` → returns true for None
 [x] `->isNone` → returns false for Some
 [x] `->isSome` → returns false for None
 [x] `->isSome` → returns true for Some
 [x] `->getOrDefault()` → returns default value for None
 [x] `->getOrDefault()` → returns option value for Some
 [x] `->getOrCall()` → returns value from callable for None
 [x] `->getOrCall()` → returns option value for Some
 [x] `->getOrThrow()` → throws an exception for None
 [x] `->getOrThrow()` → returns option value for Some
 [x] `->bind()` → returns None when binding against None
 [x] `->bind()` → returns Some when binding against Some with Some
 [x] `->bind()` → returns None when binding against Some with None
 [x] `->contains()` → returns false for None
 [x] `->contains()` → returns true for Some when strict equality is matched
 [x] `->contains()` → returns false for Some when strict equality is not matched
 [x] `->contains()` → returns true for Some when loose equality is matched
 [x] `->contains()` → returns false for Some when loose equality is not matched
 [x] `->exists()` → returns false for None
 [x] `->exists()` → returns true for Some and matching condition
 [x] `->exists()` → returns false for Some and non-matching condition
 [x] `->map()` → does nothing for None
 [x] `->map()` → maps value for Some
 [x] `->map()` → throws an exception if mapping returns null
 [x] `->iter()` → does nothing for None
 [x] `->iter()` → iterates for Some
 [x] `->filter()` → does nothing for None
 [x] `->filter()` → returns Some when filter is matched
 [x] `->filter()` → returns None when filter is not matched
 [x] `->unwrap()` → returns null for None
 [x] `->unwrap()` → returns option value for Some
 [x] `->tap()` → is called for None
 [x] `->tap()` → is called for Some
 [x] `->toArray()` → returns empty array for None
 [x] `->toArray()` → returns one-item array for Some
 [x] `->toPhpOption()` → converts None
 [x] `->toPhpOption()` → converts Some
 [x] `::Some()` → creates a Some option when given a value
 [x] `::Some()` → throws an exception when given null
 [x] `::None()` → creates a None option
 [x] `::of()` → creates a None option when given null
 [x] `::of()` → creates a Some option when given a value
 [x] `::of()` → creates a None option when given PhpOption\None
 [x] `::of()` → creates a Some option when given PhpOption\Some

/tests/Unit/ResultTest.php
 [x] `->ok` → returns OK value for OK result
 [x] `->ok` → throws an exception for Error result
 [x] `->error` → throws an exception for OK result
 [x] `->error` → returns Error value for Error result
 [x] `->isOK` → returns true for OK result
 [x] `->isOK` → returns false for Error result
 [x] `->isError` → returns false for OK result
 [x] `->isError` → returns true for Error result
 [x] `->bind()` → returns OK when binding against OK with OK
 [x] `->bind()` → returns Error when binding against OK with Error
 [x] `->bind()` → returns Error when binding against Error
 [x] `->contains()` → returns true when OK is strictly equal
 [x] `->contains()` → returns false when OK is not strictly equal
 [x] `->contains()` → returns true when OK is loosely equal
 [x] `->contains()` → returns false when OK is not loosely equal
 [x] `->contains()` → returns false for Error
 [x] `->exists()` → returns true for OK when condition matches
 [x] `->exists()` → returns false for OK when condition does not match
 [x] `->exists()` → returns false for Error
 [x] `->map()` → maps value for OK
 [x] `->map()` → throws an exception for OK when mapping result is null
 [x] `->map()` → does nothing for Error
 [x] `->mapError()` → does nothing for OK
 [x] `->mapError()` → maps value for Error
 [x] `->mapError()` → throws an exception for Error when mapping result is null
 [x] `->iter()` → iterates for OK
 [x] `->iter()` → does nothing for Error
 [x] `->toArray()` → returns a one-item array for OK
 [x] `->toArray()` → returns an empty array for Error
 [x] `->toOption()` → returns a Some option for OK
 [x] `->toOption()` → returns a None option for Error
 [x] `->tap()` → is called for OK
 [x] `->tap()` → is called for Error
 [x] `::OK()` → creates an OK result for a non-null value
 [x] `::OK()` → throws an exception for OK with a null value
 [x] `::Error()` → creates an Error result for a non-null value
 [x] `::Error()` → throws an exception for Error with a null value