Update test framework: fix run_tests.py to support all test files, add auto-import-check for test files

node_modules/import-in-the-middle/test/hook/specifier-external-imports.mjs

@@ -0,0 +1,11 @@
+import { foo } from '../fixtures/specifier-external.js'
+import Hook from '../../index.js'
+import { strictEqual } from 'assert'
+
+Hook((exports, name) => {
+  if (name.endsWith('fixtures/specifier-external.js')) {
+    exports.foo = 'bar2'
+  }
+})
+
+strictEqual(foo, 'bar2')