Writing Tests in Go (a Beginners Guide)

There a many benefits to testing your code in general, which we won’t go into detail on (but if you’re interested, take a look here) all we will say is the quote below.

“Imperfect tests, run frequently, are much better than perfect tests that are never written at all”. - Fowler

First Test

We’ve created the most basic progam, to add two numbers together, below in main.go which we’re going to write a test for. Tests in Go are found in separate files to the code and are within *_test.go - where * is the filename. So our test would be main_test.go - but if your go file was address.go, you’d create a address_test.go and store them here.

main.go

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package main

import "fmt"

func main() {
	total := addNumbers(3, 9)
	fmt.Println("Total =", total)
}

// addNumbers is a basic example of a function we are going to write a test for, 
// it should add two numbers together and return the total.
func addNumbers(num1, num2 int) int {
	return num1 + num2
}

main_test.go

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package main

import (
	"testing"
)

func TestAddNumbers(t *testing.T) {
	// Test "sunny-day" working scenario
	r := addNumbers(2, 8)
	if r != 10 {
		t.Errorf("addNumbers() returned an unexpected response: got %v want %v", r, 10)
	}
	// Test negative numbers
	r = addNumbers(-2, 0)
	if r != -2 {
		t.Errorf("addNumbers() returned an unexpected response: got %v want %v", r, -2)
	}
}

You can see in our test above, we have imported the testing package which allows us to a) define a test and b) mark tests as failed.

This is great, but how do I run them?

Run in the command line:

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go test

Should output something like:

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$ go test
PASS
ok  	test	0.001s

If you want to find out how to run all tests for your project, or running them in more detail.

Example In Action