Better testing infrastructure; Initial exports/imports/re-exports

tests/util/diff.ts

@@ -0,0 +1,30 @@
+import * as JsDiff from "diff";
+import * as chalk from "chalk";
+
+export function diff(filename: string, expected: string, actual: string): string | null {
+  const diff = JsDiff.structuredPatch(filename, filename, expected, actual, "expected", "actual", { context: 2 });
+  if (!diff.hunks.length)
+    return null;
+
+  const ret = [];
+  ret.push('--- ' + diff.oldHeader);
+  ret.push('+++ ' + diff.newHeader);
+
+  for (let i = 0; i < diff.hunks.length; i++) {
+    const hunk = diff.hunks[i];
+    ret.push(
+      '@@ -' + hunk.oldStart + ',' + hunk.oldLines
+      + ' +' + hunk.newStart + ',' + hunk.newLines
+      + ' @@'
+    );
+    ret.push.apply(ret, hunk.lines.map(line =>
+      line.charAt(0) === "+"
+        ? chalk.default.green(line)
+        : line.charAt(0) === "-"
+        ? line = chalk.default.red(line)
+        : line
+    ));
+  }
+
+  return ret.join('\n') + '\n';
+}