Add tests for missing or invalid content-type headers

test/browser/core.js

@@ -131,6 +131,19 @@ suite('SystemJS Standard Tests', function() {
     });
   });
 
+  test('Errors for bad Content-Type headers', function () {
+    return System.import('fixtures/content-type-none.json')
+    .catch(function (err) {
+      assert.ok(/missing.*content-type.*error#4/i.test(err));
+    })
+    .then(function () {
+      return System.import('fixtures/content-type-xml.json')
+    })
+    .catch(function (err) {
+      assert.ok(/unknown module type.*xml.*error#4/i.test(err));
+    })
+  });
+
   if (typeof Worker !== 'undefined')
   test('Using SystemJS in a Web Worker', function () {
     const worker = new Worker('./browser/worker.js');

test/fixtures/browser/content-type-none.json

@@ -0,0 +1,4 @@
+{
+    "ok": "content but",
+    "no": "content-type"
+}

test/fixtures/browser/content-type-xml.json

@@ -0,0 +1,3 @@
+{
+    "strange": "content-type header"
+}

test/server.cjs

@@ -84,12 +84,15 @@ http.createServer(async function (req, res) {
   let mime;
   if (filePath.endsWith('javascript.css'))
     mime = 'application/javascript';
+  else if (filePath.endsWith('content-type-xml.json'))
+    mime = 'application/xml';
   else
     mime = mimes[path.extname(filePath)] || 'text/plain';
 
-  res.writeHead(200, {
-    'content-type': mime
-  });
+  const headers = filePath.endsWith('content-type-none.json') ?
+    {} : { 'content-type': mime }
+
+  res.writeHead(200, headers);
   fileStream.pipe(res);
   await once(fileStream, 'end');
   res.end();