Writing readable tests Separating mechanics from data Alex Tercete @alextercete

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read- ability?

read- ability

understand- ability

The four elements of readability

https://www.flickr.com/photos/tychosnose/15416119182 Context WHERE

Reader’s Experience https://www.flickr.com/photos/theilr/5048464567 WHO

https://www.flickr.com/photos/thomasclaveirole/463202335 Structure HOW

Content https://www.flickr.com/photos/carinefel/13916816466 WHAT

Structure Mechanics Content Data

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[Test] public void Add_two_numbers() { var calculator = new RpnCalculator(); calculator.Push(5); calculator.Push(3); Assert.That(calculator.Add(), Is.EqualTo(8)); } [Test] public void Add_two_numbers() { var calculator = new RpnCalculator(); calculator.Push(5); calculator.Push(3); Assert.That(calculator.Add(), Is.EqualTo(8)); }

[Test] public void Subtract_two_numbers() { var calculator = new RpnCalculator(); calculator.Push(5); calculator.Push(3); Assert.That(calculator.Subtract(), Is.EqualTo(2)); } [Test] public void Add_two_numbers() { var calculator = new RpnCalculator(); calculator.Push(5); calculator.Push(3); Assert.That(calculator.Add(), Is.EqualTo(8)); } [Test] public void Subtract_two_numbers() { var calculator = new RpnCalculator(); calculator.Push(5); calculator.Push(3); Assert.That(calculator.Subtract(), Is.EqualTo(2)); }

Don’t Repeat Yourself

[SetUp] public void SetUp() { _calculator = new RpnCalculator(); _calculator.Push(5); _calculator.Push(3); } [Test] public void Add_two_numbers() { Assert.That(_calculator.Add(), Is.EqualTo(8)); } private RpnCalculator _calculator; [SetUp] public void SetUp() { _calculator = new RpnCalculator(); _calculator.Push(5); _calculator.Push(3); } [Test] public void Add_two_numbers() { Assert.That(_calculator.Add(), Is.EqualTo(8)); } [Test] public void Subtract_two_numbers() { Assert.That(_calculator.Subtract(), Is.EqualTo(2)); }

Repeat everything

[Test] public void Add_two_numbers() { var calculator = new RpnCalculator(); calculator.Push(5); calculator.Push(3); Assert.That(calculator.Add(), Is.EqualTo(8)); } [Test] public void Subtract_two_numbers() { var calculator = new RpnCalculator(); calculator.Push(5); calculator.Push(3); Assert.That(calculator.Subtract(), Is.EqualTo(2)); } [Test] public void Add_two_numbers() { var calculator = new RpnCalculator(); calculator.Push(5); calculator.Push(3); Assert.That(calculator.Add(), Is.EqualTo(8)); }

Separate mechanics from data

public void SetUp() { _calculator = new RpnCalculator(); } [Test] public void Add_two_numbers() { _calculator.Push(5); _calculator.Push(3); Assert.That(_calculator.Add(), Is.EqualTo(8)); } private RpnCalculator _calculator; [SetUp] public void SetUp() { _calculator = new RpnCalculator(); } [Test] public void Add_two_numbers() { _calculator.Push(5); _calculator.Push(3); Assert.That(_calculator.Add(), Is.EqualTo(8)); } [Test] public void Subtract_two_numbers() { _calculator.Push(5); _calculator.Push(3); Assert.That(_calculator.Subtract(), Is.EqualTo(2)); }

If it isn’t data, it must be mechanics https://www.flickr.com/photos/sarahreido/3120877348

[Test] public void Show_result_of_an_addition_on_the_display() { var stubCalculatorEngine = Substitute.For(); stubCalculatorEngine.Add(1, 2).Returns(3); var mockCalculatorDisplay = Substitute.For(); var calculator = new Calculator(stubCalculatorEngine, mockCalculatorDisplay); calculator.Type('1', '+', '2', '='); mockCalculatorDisplay.Received().Show("3"); }

[Test] public void Show_result_of_an_addition_on_the_display() { var stubCalculatorEngine = Substitute.For(); stubCalculatorEngine.Add(1, 2).Returns(3); var mockCalculatorDisplay = Substitute.For(); var calculator = new Calculator(stubCalculatorEngine, mockCalculatorDisplay); calculator.Type('1', '+', '2', '='); mockCalculatorDisplay.Received().Show("3"); }

[SetUp] public void SetUp() { _stubCalculatorEngine = Substitute.For(); _mockCalculatorDisplay = Substitute.For(); _calculator = new Calculator(_stubCalculatorEngine, _mockCalculatorDisplay); } [Test] public void Show_result_of_an_addition_on_the_display() { _stubCalculatorEngine.Add(1, 2).Returns(3); _calculator.Type('1', '+', '2', '='); _mockCalculatorDisplay.Received().Show("3"); }

Keep only what is essential to understand the test

Thanks! Alex Tercete @alextercete https://speakerdeck.com/alextercete/writing-readable-tests