public function testIsSupplier() { $this->assertTrue(Callables::isSupplier(Callables::newSupplier(function () { return null; }))); $this->assertFalse(Callables::isSupplier(Callables::newFunktion(function () { return null; }))); $this->assertFalse(Callables::isSupplier(Callables::newPredicate(function () { return null; }))); $this->assertFalse(Callables::isSupplier(Callables::newConsumer(function () { return null; }))); }