public function testAbsReturnsAbsoluteValue() { $c1 = new ComplexType($this->createRationalType(1), $this->createRationalType(2)); $c2 = new ComplexType($this->createRationalType(-1), $this->createRationalType(2)); $c3 = new ComplexType($this->createRationalType(1), $this->createRationalType(-2)); $c4 = new ComplexType($this->createRationalType(-1), $this->createRationalType(-2)); $this->assertEquals($c1->modulus(), $c1->abs()); $this->assertEquals($c1->modulus(), $c2->abs()); $this->assertEquals($c1->modulus(), $c3->abs()); $this->assertEquals($c1->modulus(), $c4->abs()); }