Unit Testing

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.