Fixed loading of external reporters in the default configuration

* Fixes #189

lib/loader.js

@@ -11,11 +11,18 @@ function Loader(options) {
 
 Loader.prototype.load = function(modulePath) {
   if ((this.alwaysImport && !modulePath.endsWith('.json')) || modulePath.endsWith('.mjs')) {
-    // The ES module spec requires import paths to be valid URLs. As of v14,
-    // Node enforces this on Windows but not on other OSes. On OS X, import
-    // paths that are URLs must not contain parent directory references.
-    const url = `file://${this.resolvePath_(modulePath)}`;
-    return this.import_(url)
+    let importSpecifier;
+
+    if (modulePath.indexOf('/') === -1) {
+      importSpecifier = modulePath;
+    } else {
+      // The ES module spec requires import paths to be valid URLs. As of v14,
+      // Node enforces this on Windows but not on other OSes. On OS X, import
+      // paths that are URLs must not contain parent directory references.
+      importSpecifier = `file://${this.resolvePath_(modulePath)}`;
+    }
+
+    return this.import_(importSpecifier)
       .then(
         mod => mod.default,
         e => {

spec/loader_spec.js

@@ -39,6 +39,21 @@ describe('loader', function() {
         });
       });
 
+      it('imports non-local modules', async function() {
+        const payload = {default: {}};
+        const requireShim = jasmine.createSpy('requireShim');
+        const importShim = jasmine.createSpy('importShim')
+          .and.returnValue(Promise.resolve(payload));
+        const loader = new Loader({requireShim, importShim});
+        loader.alwaysImport = true;
+
+        const result = await loader.load('some-module');
+
+        expect(result).toBe(payload.default);
+        expect(requireShim).not.toHaveBeenCalled();
+        expect(importShim).toHaveBeenCalledWith('some-module');
+      });
+
       it('uses require to load JSON files', async function() {
         const requireShim = jasmine.createSpy('requireShim')
           .and.returnValue(Promise.resolve());