feat: add end-to-end testing to this repository (#220)

* feat: add end-to-end testing to this repository

Part of https://github.com/ooni/probe-engine/issues/1181

Motivation: we want to run this check from the repository where
we work the most, such that it's unlikely it pauses due to inactivity,
as it may happen for less frequently touched upon repositories.

Code adapted from https://github.com/ooni/e2etesting/

* fix: correct name for main branch

internal/cmd/e2epostprocess/main.go

@@ -0,0 +1,82 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"flag"
+	"io/ioutil"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+)
+
+func fatalOnError(err error) {
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+// Measurement contains a OONI measurement.
+type Measurement struct {
+	ReportID        string  `json:"report_id"`
+	Input           *string `json:"input"`
+	SoftwareName    string  `json:"software_name"`
+	SoftwareVersion string  `json:"software_version"`
+}
+
+func main() {
+	expected := flag.Int("expected", 0, "Expected number of measurement files")
+	flag.Parse()
+	if *expected <= 0 {
+		log.Fatal("You MUST specify `-expected N`")
+	}
+	// based off https://flaviocopes.com/go-list-files/
+	var files []string
+	outputdir := "./E2E/"
+	err := filepath.Walk(outputdir, func(path string, info os.FileInfo, err error) error {
+		if strings.HasSuffix(path, ".jsonl") {
+			files = append(files, path)
+		}
+		return nil
+	})
+	fatalOnError(err)
+	if len(files) <= 0 {
+		log.Fatal("no files to process?!")
+	}
+	var found int
+	for _, file := range files {
+		data, err := ioutil.ReadFile(file)
+		fatalOnError(err)
+		measurements := bytes.Split(data, []byte("\n"))
+		for _, measurement := range measurements {
+			if len(measurement) <= 0 {
+				continue
+			}
+			var entry Measurement
+			err = json.Unmarshal(measurement, &entry)
+			fatalOnError(err)
+			log.Printf("processing: %+v", entry)
+			options := []string{
+				"run",
+				"./internal/cmd/apitool",
+				"-mode", "meta",
+				"-report-id", entry.ReportID,
+			}
+			found++
+			if entry.Input != nil {
+				options = append(options, "-input")
+				options = append(options, *entry.Input)
+			}
+			log.Printf("run: go %s", strings.Join(options, " "))
+			cmd := exec.Command("go", options...)
+			cmd.Stdout, cmd.Stderr = os.Stdout, os.Stderr
+			err = cmd.Run()
+			fatalOnError(err)
+		}
+	}
+	if found != *expected {
+		log.Fatalf("expected %d measurements, found %d measurements", *expected, found)
+	}
+}