diff --git a/lib/internal/main/test_runner.js b/lib/internal/main/test_runner.js
index cc853da7388821..b1f69b07771ac6 100644
--- a/lib/internal/main/test_runner.js
+++ b/lib/internal/main/test_runner.js
@@ -21,7 +21,7 @@ markBootstrapComplete();
 
 const options = parseCommandLine();
 
-if (isUsingInspector()) {
+if (isUsingInspector() && options.isolation === 'process') {
   process.emitWarning('Using the inspector with --test forces running at a concurrency of 1. ' +
   'Use the inspectPort option to run with concurrency');
   options.concurrency = 1;
diff --git a/lib/internal/test_runner/runner.js b/lib/internal/test_runner/runner.js
index dd167b8af0ad15..446ee8accfdba1 100644
--- a/lib/internal/test_runner/runner.js
+++ b/lib/internal/test_runner/runner.js
@@ -58,7 +58,11 @@ const {
 const { getInspectPort, isUsingInspector, isInspectorMessage } = require('internal/util/inspector');
 const { isRegExp } = require('internal/util/types');
 const { pathToFileURL } = require('internal/url');
-const { getCWDURL, kEmptyObject } = require('internal/util');
+const {
+  createDeferredPromise,
+  getCWDURL,
+  kEmptyObject,
+} = require('internal/util');
 const { kEmitMessage } = require('internal/test_runner/tests_stream');
 const {
   createTestTree,
@@ -654,7 +658,7 @@ function run(options = kEmptyObject) {
         return subtest;
       });
     };
-  } else {
+  } else if (isolation === 'none') {
     if (watch) {
       filesWatcher = watchFiles(testFiles, opts);
       runFiles = async () => {
@@ -666,7 +670,7 @@ function run(options = kEmptyObject) {
       };
     } else {
       runFiles = async () => {
-        const { promise, resolve: finishBootstrap } = Promise.withResolvers();
+        const { promise, resolve: finishBootstrap } = createDeferredPromise();
 
         await root.runInAsyncScope(async () => {
           const parentURL = getCWDURL().href;
@@ -678,13 +682,14 @@ function run(options = kEmptyObject) {
           for (let i = 0; i < testFiles.length; ++i) {
             const testFile = testFiles[i];
             const fileURL = pathToFileURL(testFile);
+            const parent = i === 0 ? undefined : parentURL;
             let threw = false;
             let importError;
 
             root.entryFile = resolve(testFile);
             debug('loading test file:', fileURL.href);
             try {
-              await cascadedLoader.import(fileURL, parentURL, { __proto__: null });
+              await cascadedLoader.import(fileURL, parent, { __proto__: null });
             } catch (err) {
               threw = true;
               importError = err;
diff --git a/src/node_options.cc b/src/node_options.cc
index 893407adcdff6c..f88495d0bbbe94 100644
--- a/src/node_options.cc
+++ b/src/node_options.cc
@@ -143,8 +143,16 @@ void EnvironmentOptions::CheckOptions(std::vector<std::string>* errors,
   }
 
   if (test_runner) {
-    if (test_isolation != "process" && test_isolation != "none") {
-      errors->push_back("invalid value for --experimental-test-isolation");
+    if (test_isolation == "none") {
+      debug_options_.allow_attaching_debugger = true;
+    } else {
+      if (test_isolation != "process") {
+        errors->push_back("invalid value for --experimental-test-isolation");
+      }
+
+#ifndef ALLOW_ATTACHING_DEBUGGER_IN_TEST_RUNNER
+      debug_options_.allow_attaching_debugger = false;
+#endif
     }
 
     if (syntax_check_only) {
@@ -163,10 +171,6 @@ void EnvironmentOptions::CheckOptions(std::vector<std::string>* errors,
       errors->push_back(
           "--watch-path cannot be used in combination with --test");
     }
-
-#ifndef ALLOW_ATTACHING_DEBUGGER_IN_TEST_RUNNER
-    debug_options_.allow_attaching_debugger = false;
-#endif
   }
 
   if (watch_mode) {