How to Mock HTTP Calls in Go (httptest)

Use net/http/httptest to create an in-memory server that handles requests without network I/O. This allows you to test HTTP handlers by sending requests to the server and asserting the response directly in your test function.

import (
	"net/http"
	"net/http/httptest"
	"testing"
)

func TestHandler(t *testing.T) {
	// Create a test server with your handler
	req := httptest.NewRequest("GET", "/", nil)
	rr := httptest.NewRecorder()

	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
		w.Write([]byte("Hello"))
	})

	// Serve the request
	handler.ServeHTTP(rr, req)

	// Assert status and body
	if status := rr.Code; status != http.StatusOK {
		t.Errorf("handler returned wrong status code: got %v want %v", status, http.StatusOK)
	}
	if rr.Body.String() != "Hello" {
		t.Errorf("handler returned unexpected body: got %v want %v", rr.Body.String(), "Hello")
	}
}

Mocking HTTP calls in Go with httptest lets you test your web server code without starting a real web server or making actual network calls. It's like running a practice game where you play both sides to check if the rules work correctly before the real match. You use it whenever you need to verify that your HTTP handlers return the correct data or status codes.