public function testTell()
{
$writer = Writer::of(2, Monoid::empty());
list($xs, $log) = $writer->chain(function ($x) use($writer) {
$log = new Monoid(['Hello, world!']);
return $writer->tell($log)->map(function ($_) use($x) {
return $x * 2;
});
})->run();
$this->assertEquals($xs, 4, 'Maps correctly.');
$this->assertEquals($log->value, ['Hello, world!'], 'Logs correctly.');
}
public function testApplicativeConstructor()
{
$this->assertEquals(Writer::of(2, Monoid::empty())->run()[0], 2, 'Constructs an applicative.');
}