test_runner: get format from parentURL as default or pass specifier a…

…rgument as fallback

lib/test/mock_loader.js

@@ -23,8 +23,8 @@ let debug = require('internal/util/debuglog').debuglog('test_runner', (fn) => {
   debug = fn;
 });
 const { createRequire, isBuiltin } = require('module');
-const { defaultResolve } = require('internal/modules/esm/resolve');
 const { defaultGetFormatWithoutErrors } = require('internal/modules/esm/get_format');
+const { defaultResolve } = require('internal/modules/esm/resolve');
 
 // TODO(cjihrig): This file should not be exposed publicly, but register() does
 // not handle internal loaders. Before marking this API as stable, one of the
@@ -97,13 +97,13 @@ async function resolve(specifier, context, nextResolve) {
   if (isBuiltin(specifier)) {
     mockSpecifier = ensureNodeScheme(specifier);
   } else {
-    const format = defaultGetFormatWithoutErrors(pathToFileURL(specifier));
+    const format = defaultGetFormatWithoutErrors(
+      pathToFileURL(context.parentURL ?? specifier)
+    );
 
     try {
-      if(format === "module") {
-        specifier = pathToFileURL(
-          defaultResolve(specifier, context)
-        ).href;
+      if (format === 'module') {
+        specifier = defaultResolve(specifier, context).url;
       } else {
         const req = createRequire(context.parentURL);
         specifier = pathToFileURL(req.resolve(specifier)).href;
@@ -240,4 +240,4 @@ function sendAck(buf, status = kMockSuccess) {
   AtomicsNotify(buf, 0);
 }
 
-module.exports = { initialize, load, resolve };
+module.exports = { initialize, load, resolve };