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Learning Test-Driven Development with Go

Tests in Go

Explore how to use Go's testing features such as subtests and table-driven tests to write clean and maintainable test code. Understand various testing options including coverage reporting and concurrency detection to improve test reliability and organization.

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Go has some fantastic features for tests that are worth mentioning.

Subtests

Subtests help us write more structured test code. Let’s use an example to understand this:

Go (1.18.2)
package subtests
import (
	"fmt"
)
type Person struct {
	age int
}
func NewPerson(age int) (*Person, error) {
	if age < 0 {
		return nil, fmt.Errorf("age cannot be less than 0")
	}
	return &Person{age: age}, nil
}

For the rest of the lesson, we’ll rely on this production function for writing tests. The NewPerson function has two branches to cover:

  • The happy one is when we provide a valid age.
  • The bad one is when we pass an invalid age.

With that being said, we have to write two test functions that we’ll call TestNewPerson_WithValidAge and TestNewPerson_WithNotValidAge. Hopefully, subtests provide us with a better approach. Let’s see this in the code below:

package subtests

import "testing"

func TestNewPerson(t *testing.T) {
	t.Run("MustReturnPerson_WhenAValidAgeIsPassed", func(t *testing.T) {
		age := 18
		got, err := NewPerson(age)
		if err != nil {
			t.Errorf("err not expected but got %q", err.Error())
		}
		if got == nil {
			t.Fatal("got expected to be not nil")
		}
		if got.age != age {
			t.Errorf("age expected to be %d but got %d", age, got.age)
		}
	})

	t.Run("MustReturnErr_WhenANotValidAgeIsPassed", func(t *testing.T) {
		age := -5
		expectedErr := "age cannot be less than 0"
		got, err := NewPerson(age)
		if err == nil {
			t.Fatal("err not expected to be nil")
		}
		if err.Error() != expectedErr {
			t.Errorf("expected err was %q but got %q", expectedErr, err.Error())
		}
		if got != nil {
			t.Error("got expected to be nil")
		}
	})
}
Example of subtests

Thanks to the t.Run function, we’re able to create a parent-child structure in our test code. In fact, the ...