Question

Unit testing allows us to test a http.HandlerFunc directly without running any middleware, routers, or any other type of code that might otherwise wrap the function.

package main

import (
  "fmt"
  "net/http"
)

func HelloWorld(res http.ResponseWriter, req *http.Request) {
  fmt.Fprint(res, "Hello World")
}

func main() {
  http.HandleFunc("/", HelloWorld)
  http.ListenAndServe(":3000", nil)
}

This is the test file. It should be placed in the same directory as your application and name main_test.go .

package main

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

func Test_HelloWorld(t *testing.T) {
  req, err := http.NewRequest("GET", "http://example.com/foo", nil)
  if err != nil {
    t.Fatal(err)
  }

  res := httptest.NewRecorder()
  HelloWorld(res, req)

  exp := "Hello World"
  act := res.Body.String()
  if exp != act {
    t.Fatalf("Expected %s gog %s", exp, act)
  }
}

Exercises

1. Change the output of HelloWorld to print a parameter and then test that the parameter is rendered.
2. Create a POST request and test that the request is properly handled.