test: repl tab completion test

It checks that `eval` is called with `.scope` as an input string.

PR-URL: #5534
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-repl-eval-scope.js

@@ -0,0 +1,23 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const repl = require('repl');
+
+{
+  const stream = new common.ArrayStream();
+  const options = {
+    eval: common.mustCall((cmd, context) => {
+      assert.strictEqual(cmd, '.scope\n');
+      assert.deepStrictEqual(context, {animal: 'Sterrance'});
+    }),
+    input: stream,
+    output: stream,
+    terminal: true
+  };
+
+  const r = repl.start(options);
+  r.context = {animal: 'Sterrance'};
+
+  stream.emit('data', '\t');
+  stream.emit('.exit\n');
+}