in property based testing we test the properties of the domain we are working on, example, if we are working on numbers, those properties can be commutative law, associative law etc

property testing of roman numbers

func TestPropertiesOfConversion(t *testing.T) {
	assertion := func(arabic int) bool {
		roman := ConvertToRoman(arabic)
		fromRoman := ConvertToArabic(roman)
		return fromRoman == arabic
	}

	if err := quick.Check(assertion, nil); err != nil {
		t.Error("failed checks", err)
	}
}

We're using the testing/quick package from the standard library

Reading from the bottom, we provide quick.Check a function that it will run against a number of random inputs, if the function returns false it will be seen as failing the check.

Our assertion function above takes a random number and runs our functions to test the property.

Property based tests

• Built into the standard library
• If you can think of ways to describe your domain rules in code, they are an excellent tool for giving you more confidence
• Force you to think about your domain deeply
• Potentially a nice complement to your test suite