README.md

Testing

Go comes with a simple test suite. We'll start by writing a simple test and placing it in a file called httpd_test.go.

The go build tool ignores files ending with _test.go in the normal build process. While the go test tool looks for them and executes every test function in them.

Simple Test

Let's start simple, write the following in httpd_test.go

package main

import (
	"testing"
)

func TestHome(t *testing.T) {
}

To be a test function, it should start with Test and except one parameter of type *testing.T.

Once you have that, execute

go test -v

You should see your first passing test!

Handler Test

To test our HTTP server we have two options. We can either run it as a process and then issue HTTP requests to it, or we can test the handler functions directly.

We'll go with the second approach and use the net/http/httptest package. Which lets us create new requests and http.ResponseWriter that records what was written to it.

If you look in the documentation of httptest you'll see:

func NewRequest(method, target string, body io.Reader) *http.Request

The net/http/httptest defines NewRequest. In Go, we don't have constructors like in other OO languages, instead we define New<TYPE> function that returns a new object.

Variable Definitions

Before we go on, we need to see how we can define new variables. We can either use var as in

var i int

i is of type int (which is 64 bits on my machine), it will be initialize to the zero value of its type, which is the number 0.

We can also assign a value when we define the variable

var i int = 42

The last form, and the most common one, it to let the Go compiler infer the variable type from the value.

i := 42

We can also assign multiple variables in the same line

i, s := 42, "hello"

Functions in Go can return multiple values, and then we can use this multiple assignment.

val1, val2 = someFunction()

It's very common in Go that the last value a functions returns is an error code. We don't use exceptions as in Python/C++/Java...

if Statement

Go has the usual if statement.

if i > 0 {
    fmt.Println("i is big")
}

We don't need to place () around the condition.

We can combine conditions with || for or, && for and and negate them with !

if i > 0 && i < 10 {
    fmt.Println("i is just right")
}

Go has the usual comparison operators: ==, !=, >, >=, < and <=.

We can also assign and check in one if statement. This is very common combined with error checking.

if err := writeMetric("num_errors", 0); err != nil {
	fmt.Println(err)
}

Exercise

Change TestHome to call handler and check that we get שלום Gophers back.

Hint: See ResponseRecorder example.

Solution