Unit Testing By Example

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@aﬁlina Unit Testing by Example SunshinePHP, Miami - February 4, 2017

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

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

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You Don’t Become an Expert Overnight

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You Don’t Start With 100% Coverage

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Testing Without Automation

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

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

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

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Shopping Cart

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

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

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Regression Testing

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

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

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

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

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

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

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Data From CSV

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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]);

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

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

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

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How Many Cases?

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Cyclomatic Complexity

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

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Condition Loop

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

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

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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.