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/duplicate-exports-explicit.mjs

@@ -0,0 +1,13 @@
+import * as lib from '../fixtures/duplicate-explicit.mjs'
+import { strictEqual } from 'assert'
+import Hook from '../../index.js'
+
+Hook((exports, name) => {
+  if (name.endsWith('duplicate-explicit.mjs')) {
+    strictEqual(exports.foo, 'c')
+    exports.foo += '-wrapped'
+  }
+})
+
+// foo should not be exported because there are duplicate exports
+strictEqual(lib.foo, 'c-wrapped')