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Go 101 : Testing simple Go server

Code we will be testing : main.go

package main

import (
	"fmt"
	"log"
	"net/http"
)

func main() {
	http.HandleFunc("/", helloWorldEndPoint)
	fmt.Println("Server :  http://localhost:8080")
	log.Fatal(http.ListenAndServe(":8080", nil))
}

func helloWorldEndPoint(writer http.ResponseWriter, request *http.Request) {
	fmt.Fprintf(writer, "hello world")
}

• Create a file with name _test.go, these files are ignore by compiler
• Write a func matching func TestXxx(*testing.T) where Xxx does not start with a lowercase letter.
• The function name serves to identify the test routine.

To run the test :

go test

Writing Test‌

Inorder to test the handler, we call it by passing http.ResponseWriter and *http.Request to create a new Request

req, err := http.NewRequest(http.MethodGet,"http://localhost:8080/",nil)     

if err != nil {  
    t.Fatalf("Could not create a request %v", err)
}

• To record the response from the writer

rec := httptest.NewRecorder()

• To verify

helloWorldEndPoint(rec, req)

if rec.Code != http.StatusOK {  
    t.Errorf("accepted status 200, got %v", rec.Code)
}

// checking the msg returned
if !strings.Contains(rec.Body.String(), "hello world") {  
    t.Errorf("unexpected body in response %q", rec.Body.String())
}

Full code main_test.go

package main
import (  
    "net/http"
    "net/http/httptest"   
    "strings"  
    "testing"
)

func TestHandler(t *testing.T) {  

    req, err := http.NewRequest(http.MethodGet,"http://localhost:8080/",nil) 
    if err != nil {   
        t.Fatalf("Could not create a request %v", err) 
    } 

    rec := httptest.NewRecorder() 

    helloWorldEndPoint(rec, req) 
    if rec.Code != http.StatusOK {   
        t.Errorf("accepted status 200, got %v", rec.Code) 
    } 

    if !strings.Contains(rec.Body.String(), "hello world") {   
        t.Errorf("unexpected body in response %q", rec.Body.String()) 
    }
}

I hope you like this article !