main_test.go

package main

import (
	"fmt"
	"io"
	"math/rand"
	"net"
	"net/http"
	"os"
	"strconv"
	"syscall"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

func Test_Main(t *testing.T) {
	if _, ok := os.LookupEnv("ENABLE_MONGO_TESTS"); !ok {
		t.Skip("ENABLE_MONGO_TESTS env variable is not set")
	}

	port := chooseRandomUnusedPort()
	os.Args = []string{"test", "--port=" + strconv.Itoa(port), "--dbg",
		"--mongo-uri=mongodb://localhost:27017/",
		"--mongo-db=test_ureadability",
		"--frontend-dir=web",
	}

	done := make(chan struct{})
	go func() {
		<-done
		e := syscall.Kill(syscall.Getpid(), syscall.SIGTERM)
		assert.NoError(t, e)
	}()

	finished := make(chan struct{})
	go func() {
		main()
		close(finished)
	}()

	// defer cleanup because assert check below can fail
	defer func() {
		close(done)
		<-finished
	}()

	waitForHTTPServerStart(port)
	resp, err := http.Get(fmt.Sprintf("http://localhost:%d/api/ping", port))
	require.NoError(t, err)
	defer resp.Body.Close()
	assert.Equal(t, 200, resp.StatusCode)
	body, err := io.ReadAll(resp.Body)
	require.NoError(t, err)
	assert.Equal(t, "pong", string(body))
}

func chooseRandomUnusedPort() (port int) {
	for range 10 {
		port = 40000 + int(rand.Int31n(10000))
		if ln, err := net.Listen("tcp", fmt.Sprintf(":%d", port)); err == nil {
			_ = ln.Close()
			break
		}
	}
	return port
}

func waitForHTTPServerStart(port int) {
	// wait for up to 10 seconds for server to start before returning it
	client := http.Client{Timeout: time.Second}
	for range 100 {
		time.Sleep(time.Millisecond * 100)
		if resp, err := client.Get(fmt.Sprintf("http://localhost:%d", port)); err == nil {
			_ = resp.Body.Close()
			return
		}
	}
}