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
   http://foolab.ca
   @foolabca
   Unit Testing
   by Example
   ConFoo - February 26, 2014
   

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2. FooLab
   Objectives
   • Make testing enjoyable.
   • Make it useful.
   • Reduce pre-release stress.
   2
   

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3. FooLab
   Anna Filina
   3
   • I help projects ship on time.
   • I train and mentor developers.
   • I code and optimize.
   

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4. FooLab
   You don’t need
   100% coverage
   

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5. FooLab
   You don’t become an
   expert overnight
   

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6. FooLab
   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);
   }
   6
   

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7. FooLab
   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());
   7
   

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8. FooLab
   Step 2: improve code
   public function getShipping()
   {
   if ($this->getSubtotal() >= 40) {
   return 0;
   }
   else {
   return 15;
   }
   }
   8
   

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9. FooLab
   Test both cases
   $item = new CartItem("Skyrim", 30);
   $item->setQuantity(1);
   $cart->addItem($item);
   $this->assertEquals(15, $cart->getShipping());
   $this->assertEquals(45, $cart->getTotal());
   9
   

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10. FooLab
    Step 3: write code
    public function getTotal()
    {
    ...
    $taxes = $this->getApplicableTaxes();
    foreach ($taxes as $tax)
    {
    $total += $subtotal * $tax->getPercent();
    }
    ...
    }
    10
    

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11. FooLab
    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
    11
    

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12. FooLab
    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());
    12
    

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13. FooLab
    Advantages
    • More tests.
    • Easy to write.
    • Never fall too far.
    13
    

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14. FooLab
    Step 4: before (TDD)
    $import = new CatalogImport();
    $products = $import->parseFromCsv('test_catalog.csv');
    $this->assertInternalType('array', $products);
    $this->assertCount(2, $products);
    $this->assertArrayHasKey('name', products[0]);
    $this->assertArrayHasKey('price', products[0]);
    14
    

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15. FooLab
    Tips
    • How it’s not supposed to
    work.
    • Plan for exceptions.
    • Focus on realistic
    scenarios.
    15
    

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16. FooLab
    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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