Minor bugfixes. (#8)

* Strict types.

* Minor bug fix.

* Add test for exception.

* Update readme.

* Update travis build process.

Author: Ekman

.travis.yml

@@ -1,6 +1,16 @@
 language: php
+
 php:
   - '7.1'
   - '7.2'
-before_script: composer install
+
+install: composer install --no-interaction --classmap-authoritative
+
 script: vendor/bin/phpunit
+
+notifications:
+  email: false
+
+cache:
+  directories:
+    - $HOME/.composer

README.md

@@ -16,25 +16,39 @@ composer require nekman/luhn-algorithm
 
 ## Usage
 
-Use the class like this:
-
+In order to instantiate a new instance of the library, use the factory:
+ 
+ ```php
+ use Nekman\LuhnAlgorithm\LuhnAlgorithmFactory;
+ 
+ $luhn = LuhnAlgorithmFactory::create();
+ ```
+
+You can find [the public interface of the library in the `LuhnAlgorithmInterface`](src/Contract/LuhnAlgorithmInterface.php).
+
+[The `Number` class](src/Number.php) is a container class that holds the actual number and the check digit. It does no validation
+nor does it calculate the check digit. To simplify the process of validating a number you can use the
+named constructor `Number::fromString()` like this:
+ 
 ```php
-use Nekman\LuhnAlgorithm\LuhnAlgorithmFactory;
 use Nekman\LuhnAlgorithm\Number;
 
-$luhn = LuhnAlgorithmFactory::create();
+// Assume $creditCard is from a form.
+$number = Number::fromString($creditCard);
 
-// Validate a credit card number entered in a form.
-$ccNumber = Number::fromString($creditCard);
-if ($luhn->isValid($ccNumber)) {
-	// Credit card number is valid.
+if ($luhn->isValid($number)) {
+    // Number is valid.
 }
+```
+
+Alternatively, if you want to calculate the checksum or check digit for a number:
+
+```php
+use Nekman\LuhnAlgorithm\Number;
 
-// These methods are used internally by the library. You're free
-// to make use of them as well.
 $number = new Number(12345);
 
 $checksum = $luhn->calcChecksum($number);
 
 $checkDigit = $luhn->calcCheckDigit($number);
-```
+```

src/Contract/LuhnAlgorithmInterface.php

@@ -23,6 +23,8 @@
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
 
+declare(strict_types=1);
+
 namespace Nekman\LuhnAlgorithm\Contract;
 
 /**

src/Contract/NumberInterface.php

@@ -23,6 +23,8 @@
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
 
+declare(strict_types=1);
+
 namespace Nekman\LuhnAlgorithm\Contract;
 
 /**

src/LuhnAlgorithm.php

@@ -23,6 +23,8 @@
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
 
+declare(strict_types=1);
+
 namespace Nekman\LuhnAlgorithm;
 
 use Nekman\LuhnAlgorithm\Contract\LuhnAlgorithmInterface;
@@ -39,7 +41,7 @@ class LuhnAlgorithm implements LuhnAlgorithmInterface
     public function isValid(NumberInterface $number): bool
     {
         if ($number->getCheckDigit() === null) {
-            throw new \InvalidArgumentException("Check digit cannot be null.");
+            throw new \InvalidArgumentException("Check digit is null.");
         }
 
         $checksum = $this->calcChecksum($number);
@@ -71,16 +73,17 @@ public function calcCheckDigit(NumberInterface $number): int
     public function calcChecksum(NumberInterface $number): int
     {
         $number = (string) $number->getNumber();
-        $nDigits = strlen($number);
-        $checksum = 0;
+        // Need to account for the check digit.
+        $nDigits = strlen($number) + 1;
         $parity = $nDigits % 2;
+        $checksum = 0;
 
-        for ($i = 0; $i < $nDigits; $i++) {
+        for ($i = 0; $i < $nDigits - 1; $i++) {
             $digit = (int) $number[$i];
 
-            // Every other digit, starting from the leftmost,
+            // Every other digit, starting from the rightmost,
             // shall be doubled.
-            if (($i % 2) !== $parity) {
+            if (($i % 2) === $parity) {
                 $digit *= 2;
 
                 if ($digit > 9) {

src/LuhnAlgorithmFactory.php

@@ -23,6 +23,8 @@
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
 
+declare(strict_types=1);
+
 namespace Nekman\LuhnAlgorithm;
 
 use Nekman\LuhnAlgorithm\Contract\LuhnAlgorithmInterface;

src/Number.php

@@ -23,6 +23,8 @@
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
 
+declare(strict_types=1);
+
 namespace Nekman\LuhnAlgorithm;
 
 use Nekman\LuhnAlgorithm\Contract\NumberInterface;

tests/LuhnAlgorithmTest.php

@@ -60,6 +60,22 @@ public function provideIsValid_success()
         ];
     }
 
+    /**
+     * @dataProvider provideIsValid_failure
+     */
+    public function testIsValid_failure($number, $exception)
+    {
+        $this->expectException($exception);
+        $this->luhn->isValid($number);
+    }
+
+    public function provideIsValid_failure()
+    {
+        return [
+            [new Number(123, null), \InvalidArgumentException::class],
+        ];
+    }
+
     /**
      * @dataProvider provideCalcChecksum_success
      */