Unit Testing by Example

Everyone tells you that you need to write tests. You tried it, but your tests ended up not very useful and consumed valuable time. What to test? What conditions to write? Through realistic examples, this presentation will take you from var_dump() and ease you into the testing business. All this without losing sight of the tight deadlines. You will come out of this presentation with a renewed interest in writing unit tests.

Transcript

1. foolab.ca | @foolabca
   Unit Testing
   by Example
   IPC, Berlin - June 8, 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 0.5
    1 =>
    array (size=2)
    'name' => string 'QST' (length=3)
    'percent' => float 0.9975
    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(0.5, $gst->getPercent());
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16. Advantages
    • More tests.
    • Easy to write.
    • Never fall too far.
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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.
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20. Don't waste time
    $total = 5;
    $this->assertNotNull($total);
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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
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22. Cyclomatic
    Complexity
    

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23. Execution Paths
    public function getShipping()
    {
    if ($this->subtotal >= 50) {
    return 0;
    }
    return $this->shipping;
    }
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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';
    }
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26. Multiple times
    $total = 0;
    foreach ($products as $product) {
    $total = $product->price * $product->quantity;
    }
    if ($total > 0) {
    echo 'found';
    }
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27. Services
    • Development: PHP, JS, etc.
    • Fix problems: bugs, performance, etc.
    • Workshops: testing, Symfony, AngularJS
    • Advisor: testing strategy, architecture, etc.
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