Add test runner

Makefile

@@ -45,4 +45,7 @@ fmt: node_modules
 	go fmt
 	clang-format msg.proto -i
 
+test:
+	node test.js
+
 .PHONY: lint clean distclean

test.js

@@ -0,0 +1,35 @@
+#!/usr/bin/env node
+// Do not include this file from other parts of the code. We use node to
+// bootstrap a test runner.
+
+const fs = require("fs");
+const path = require("path");
+const { execFileSync } = require("child_process");
+
+const testdataDir = path.join(__dirname, "testdata");
+const denoFn = path.join(__dirname, "deno");
+const files = fs
+  .readdirSync(testdataDir)
+  .filter(fn => fn.endsWith(".out"))
+  .map(fn => path.join(testdataDir, fn));
+
+function deno(inFile) {
+  let args = [inFile];
+  console.log("deno", ...args);
+  return execFileSync(denoFn, args);
+}
+
+for (const outFile of files) {
+  const inFile = outFile.replace(/\.out$/, "");
+  let stdoutBuffer = deno(inFile);
+  let outFileBuffer = fs.readFileSync(outFile);
+  if (0 != Buffer.compare(stdoutBuffer, outFileBuffer)) {
+    throw Error(`test error
+--- stdoutBuffer - ${inFile}
+${stdoutBuffer.toString()}
+--- outFileBuffer - ${outFile}
+${outFileBuffer.toString()}
+---------------------
+    `);
+  }
+}