public function testGravityCorrection()
{
$this->assertEquals(1.0562227410997, Beercalc::gravityCorrection(100.4, 1.05, 60));
$this->assertEquals(null, Beercalc::gravityCorrection(100.4, "asdf", 60));
$this->assertEquals(null, Beercalc::gravityCorrection("asdf", 1.05, 60));
$this->assertEquals(null, Beercalc::gravityCorrection("asdf", "asdf", 60));
$this->assertEquals(null, Beercalc::gravityCorrection("asdf", 1.05, "asdf"));
$this->assertEquals(null, Beercalc::gravityCorrection(100.4, 1.05, "asdf"));
$this->assertEquals(null, Beercalc::gravityCorrection("asdf", "asdf", "asdf"));
}