Re-factor a setBirthDate method for cleaner code

original.php

    public function setBirthDate($birthDate) {
        // Allow setting with DateTime object or string date
        // TODO: Check if object is a subclass of DateTime, watch out for namespaces
        $this->birthDate = is_object($birthDate) ? $birthDate : (!empty($birthDate) ? new \DateTime($birthDate) : null);
        return $this;
    }

refactored.php

    public function setBirthDate($birthDate) {
        if (empty($birthDate)) { return $this; }

        return ($birthDate instanceof \DateTime)
             ? $this->setBirthDateFromDateTime($birthDate)
             : $this->setBirthDateFromString($birthDate);
    }

    public function setBirthDateFromDateTime(\DateTime $birthDate) {
        $this->birthDate = $birthDate;
        return $this;
    }

    public function setBirthDateFromString($birthDate) {
        if (false === date_create($birthDate)) {
            throw new exception\InvalidArgumentException(sprintf('Invalid date string specified: "%s"', $birthDate));
        }

        $this->birthDate = new \DateTime($birthDate);
        return $this;
    }

unit-tests.php

    /**
     * @test
     */
    public function Can_Set_Birth_Date_From_DateTime() {
        $birthDate= new \DateTime('2003-02-03');
        $patient  = new Patient();

        $patient->setBirthDateFromDateTime($birthDate);
        $this->assertEquals($birthDate, $patient->getBirthDate());
    }

    /**
     * @test
     */
    public function Can_Set_Birth_Date_From_DateTime_Inferred_By_Type() {
        $birthDate= new \DateTime('2003-02-03');
        $patient  = new Patient();

        $patient->setBirthDate($birthDate);
        $this->assertEquals($birthDate, $patient->getBirthDate());
    }

    /**
     * @test
     */
    public function Can_Set_Birth_Date_From_String_Inferred_By_Type() {
        $birthDate= '2003-02-03';
        $patient  = new Patient();

        $patient->setBirthDate($birthDate);
        $this->assertEquals(new \DateTime($birthDate), $patient->getBirthDate());
    }

    /**
     * @test
     * @expectedException   ets\model\data\exception\InvalidArgumentException
     */
    public function Set_Birth_Date_Inferred_By_Type_Given_A_Non_DateTime_Non_String_Should_Throw_Exception() {
        $birthDate= (integer) 500;
        $patient  = new Patient();
        $patient->setBirthDate($birthDate);
    }

    /**
     * @test
     * @expectedException   ErrorException
     */
    public function Non_DateTime_Given_To_SetBirthDateFromDateTime_Throws_ErrorException() {
        $birthDate= new \stdClass();
        $patient  = new Patient();
        $patient->setBirthDateFromDateTime($birthDate);
    }

    /**
     * @test
     */
    public function Can_Set_Birth_Date_From_String() {
        $birthDate= '2003-02-03';
        $patient  = new Patient();
        $patient->setBirthDateFromString($birthDate);
        $this->assertEquals(new \DateTime($birthDate), $patient->getBirthDate());
    }

    /**
     * @test
     * @expectedException   ets\model\data\exception\InvalidArgumentException
     */
    public function Non_Parseable_String_Given_To_SetBirthDateFromString_Throws_Exception() {
        $birthDate= 'LOL......LOL';
        $patient  = new Patient();
        $patient->setBirthDateFromString($birthDate);
    }