feat(QA): add test cases for websteps vs webconnectivity (#583)

This pull request introduces a set of Node.js scripts for performing A/B comparison of websteps and webconnectivity as described in https://github.com/ooni/probe/issues/1805. Rather than using Jafar, I ended up using `miniooni`'s `--censor` command line flag introduced in [v3.12.0-alpha.1](https://github.com/ooni/probe-cli/releases/tag/v3.12.0-alpha.1). The main reason for doing so is that it's simpler to run tests without requiring root access and Linux _and_ Docker (e.g., I did not develop part of this diff using Linux). Additionally, I choose to use Node.js rather than extending the existing Python framework for QA, because I found Node.js easier when working with JSON data.

QA/lib/runner.mjs

@@ -0,0 +1,92 @@
+// This file contains code for running test cases.
+
+import child_process from "child_process"
+import crypto from "crypto"
+import fs from "fs"
+import path from "path"
+
+// tempFile returns the name of a temporary file. This function is
+// not as secure as using mktemp but it does not matter in this
+// context. We just need to create file names in the local directory
+// with enough entropy that every run has a different name.
+//
+// See https://stackoverflow.com/questions/7055061 for an insightful
+// discussion about creating temporary files in node.
+function tempFile(suffix) {
+    return path.join(`tmp-${crypto.randomBytes(16).toString('hex')}.${suffix}`)
+}
+
+// exec executes a command. This function throws on failure. The stdout
+// and stderr should be console.log-ed once the command returns.
+function exec(command) {
+    console.log(`+ ${command}`)
+    child_process.execSync(command)
+}
+
+// writeCensorJsonFile writes a censor.json file using a file name
+// containing random characters and returns the file name.
+function writeCensorJsonFile(testCase) {
+    const fileName = tempFile("json")
+    fs.writeFileSync(fileName, JSON.stringify(testCase.blocking))
+    return fileName
+}
+
+// readReportFile reads and parses the report file, thus returning
+// the JSON object contained inside the report file.
+function readReportFile(reportFile) {
+    const data = fs.readFileSync(reportFile, { "encoding": "utf-8" })
+    return JSON.parse(data)
+}
+
+// runExperiment runs the given test case with the given experiment.
+function runExperiment(testCase, experiment, checker) {
+    console.log(`## running: ${testCase.name}.${experiment}`)
+    console.log("")
+    const censorJson = writeCensorJsonFile(testCase)
+    const reportJson = tempFile("json")
+    // Note: using -n because we don't want to submit QA checks.
+    exec(`./miniooni -n --censor ${censorJson} -o ${reportJson} -i ${testCase.input} ${experiment}`)
+    console.log("")
+    // TODO(bassosimone): support multiple entries per file
+    const report = readReportFile(reportJson)
+    const analysisResult = checker(testCase, experiment, report)
+    console.log("")
+    console.log("")
+    if (analysisResult !== true && analysisResult !== false) {
+       console.log("the analysis function returned neither true nor false")
+       process.exit(1)
+    }
+    return analysisResult
+}
+
+// recompileMiniooni recompiles miniooni if needed.
+function recompileMiniooni() {
+    exec("go build -v ./internal/cmd/miniooni")
+}
+
+// runTestCase runs the given test case.
+//
+// A test case is an object with the following fields:
+//
+// - name (string): the name of the test case;
+//
+// - description (string): a description of the test case;
+//
+// - input (string): the input to pass to the experiment;
+//
+// - blocking (object): a blocking specification (i.e., the
+// serialization of a filtering.TProxyConfig struct);
+//
+// - experiments (object): the keys are names of nettests
+// to run and the values are functions taking as their
+// unique argument the experiment's test_keys.
+export function runTestCase(testCase) {
+    recompileMiniooni()
+    console.log("")
+    console.log(`# running: ${testCase.name}`)
+    let result = true
+    for (const [name, checker] of Object.entries(testCase.experiments)) {
+        result = result && runExperiment(testCase, name, checker)
+    }
+    return result
+}