Unit Testing By Example

Everyone tells you that you need to test. You know the theory, but you don't know where to begin. What to test? What cases to write? Through realistic and pragmatic examples, this presentation will take you away from var_dump and ease you into the testing business until you're ready to do TDD. All this without losing sight of the tight deadlines.

Transcript

1. foolab.ca | @foolabca
   Unit Testing
   by Example
   FrOSCon, Sankt Augustin - August 22, 2015
   

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2. Anna Filina
   • Developer
   • Problem solver
   • Teacher
   • Advisor
   2
   

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3. Objectives
   • Make testing enjoyable.
   • Make it useful.
   • Reduce pre-release stress.
   3
   

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4. You don’t become an
   expert overnight
   

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5. You don’t start with
   100% coverage
   

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6. Testing without
   automation
   

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7. Step 1: found bug
   $item = new CartItem("Skyrim", 30);
   $item->setQuantity(0.1);
   $this->assertEquals(1, $item->getQuantity());
   7
   

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8. Step 1: found bug
   $item = new CartItem("Skyrim", 30);
   $item->setQuantity(0.1);
   $this->assertEquals(1, $item->getQuantity());
   public function setQuantity($qty)
   {
   $this->qty = ceil($qty);
   }
   8
   

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9. Regression Testing
   

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10. Step 2: improve code
    $item = new CartItem("Skyrim", 30);
    $item->setQuantity(2);
    $cart->addItem($item);
    $this->assertEquals(0, $cart->getShipping());
    $this->assertEquals(60, $cart->getTotal());
    10
    

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11. Step 2: improve code
    public function getShipping()
    {
    if ($this->getSubtotal() >= 40) {
    return 0;
    }
    else {
    return 15;
    }
    }
    11
    

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12. Test both cases
    $item = new CartItem("Skyrim", 30);
    $item->setQuantity(1);
    $cart->addItem($item);
    $this->assertEquals(15, $cart->getShipping());
    $this->assertEquals(45, $cart->getTotal());
    12
    

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13. Step 3: write code
    public function getTotal()
    {
    //...
    $taxes = $this->getApplicableTaxes();
    foreach ($taxes as $tax)
    {
    $total += $subtotal * $tax->getPercent();
    }
    //...
    }
    13
    

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14. Step 3: write code
    array (size=2)
    0 =>
    array (size=2)
    'name' => string 'GST' (length=3)
    'percent' => float 0.05
    1 =>
    array (size=2)
    'name' => string 'QST' (length=3)
    'percent' => float 0.09975
    14
    

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15. Step 3: write code
    $cart = new Cart();
    $taxes = $cart->getApplicableTaxes();
    $this->assertInternalType('array', $taxes);
    $this->assertCount(2, $taxes);
    $gst = $taxes[0];
    $this->assertEquals(0.05, $gst->getPercent());
    15
    

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16. Advantages
    • More tests.
    • Easy to write.
    • Never fall too far.
    16
    

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17. Data from CSV
    

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18. Step 4: before (TDD)
    $import = new CatalogImport();
    $products = $import->parseFromCsv('catalog.csv');
    $this->assertInternalType('array', $products);
    $this->assertCount(2, $products);
    $this->assertArrayHasKey('name', $products[0]);
    $this->assertArrayHasKey('price', $products[0]);
    18
    

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19. Tips
    • How it’s not supposed to work.
    • Plan for exceptions.
    • Focus on realistic scenarios.
    19
    

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20. Don't waste time
    $total = 5;
    $this->assertNotNull($total);
    20
    

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21. Recap
    • Testing takes practice
    • Write tests when you see
    a bug
    • Write tests when you
    improve code

    • Write tests as you write
    new code
    • Write tests before you
    write code
    • Test unexpected
    scenarios
    21
    

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22. Cyclomatic Complexity
    22
    

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23. Execution Paths
    public function getShipping()
    {
    if ($this->subtotal >= 50) {
    return 0;
    }
    return $this->shipping;
    }
    23
    

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24. Example
    24
    start
    product loop free shipping? gift wrap?
    end
    

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25. Zero times
    foreach ($products as $product) {
    $total = $product->price * $product->quantity;
    }
    if ($total > 0) {
    echo 'found';
    }
    25
    

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26. Multiple times
    $total = 0;
    foreach ($products as $product) {
    $total = $product->price * $product->quantity;
    }
    if ($total > 0) {
    echo 'found';
    }
    26
    

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27. Anna Filina
    • Development: PHP, JS, etc.
    • Fix problems: bugs, performance, etc.
    • Workshops: testing, Symfony, AngularJS, API, etc.
    • Advisor: testing strategy, legacy code, etc.
    27
    

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28. @afilina afilina.com
    

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