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. @afilina
   Unit Testing
   by Example
   Southeast Valley .NET UG - March 23, 2017
   

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2. Anna Filina
   • Project rescue expert
   • Dev, trainer, speaker
   • 1 company
   • 2 conferences
   

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

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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. Manually
   • Check database
   • var_dump
   • Only what changed
   • "Good enough" is subjective
   

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8. Problems
   • Last-minute bugs
   • Discovered by customers
   • Afraid of the code
   

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9. Automated
   • Control
   • Discover bugs
   • Confidence
   • More features, fewer bugs
   

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10. $qty = 0.1
    

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11. Step 1: Found Bug
    $item = new CartItem("Overwatch", 30);
    $item->setQuantity(0.1);
    $this->assertEquals(1, $item->getQuantity());
    

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12. Step 1: Found Bug
    $item = new CartItem("Overwatch", 30);
    $item->setQuantity(0.1);
    $this->assertEquals(1, $item->getQuantity());
    public function setQuantity($qty)
    {
    $this->qty = ceil($qty);
    }
    

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13. Too Simple?
    • Prevent future breaks
    • Why code is written this way
    • Same effort as comments
    

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14. Regression Testing
    

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15. Step 2: Improve Code
    $item = new CartItem("Overwatch", 30);
    $item->setQuantity(2);
    $cart->addItem($item);
    $this->assertEquals(0, $cart->getShipping());
    

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16. Step 2: Improve Code
    public function getShipping()
    {
    if ($this->subtotal >= 40) {
    return 0;
    }
    else {
    return 15;
    }
    }
    

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17. Test Both Cases
    $item = new CartItem("Overwatch", 30);
    $item->setQuantity(1);
    $cart->addItem($item);
    $this->assertEquals(15, $cart->getShipping());
    

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

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19. Step 3: New 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
    

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20. Step 3: New Code
    $cart = new Cart();
    $taxes = $cart->getApplicableTaxes();
    $this->assertCount(2, $taxes);
    $gst = $taxes[0];
    $this->assertEquals(0.05, $gst['percent']);
    

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

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22. Data From CSV
    

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

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24. A New Mindset
    • Write less code
    • Stay focused
    • Elegant code
    • Works right away
    

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

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26. Don't Waste Time
    $total = 5;
    $this->assertNotNull($total);
    

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27. How Many Cases?
    

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28. Cyclomatic Complexity
    

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29. Execution Paths
    public function getShipping()
    {
    if ($this->subtotal >= 40) {
    return 0;
    }
    return $this->shipping;
    }
    

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30. Condition
    Loop
    

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

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

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33. API Testing
    $this->assertJsonStringEqualsJsonString('
    {
    "data": [
    {
    "slug": "fallout4",
    "name": "Fallout 4"
    }
    ]
    }
    ', $response);
    

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34. 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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35. Testing =

    Preemptive Debugging
    

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36. @afilina afilina.com
    

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