diff --git a/dom/media/test/test_mediarecorder_record_4ch_audiocontext.html b/dom/media/test/test_mediarecorder_record_4ch_audiocontext.html
index d26da7797019..e25d18d93360 100644
--- a/dom/media/test/test_mediarecorder_record_4ch_audiocontext.html
+++ b/dom/media/test/test_mediarecorder_record_4ch_audiocontext.html
@@ -56,7 +56,8 @@ function startTest() {
     }
     totalBlobSize += e.data.size;
     ok(totalBlobSize > 0, 'check the totalBlobSize');
-    is(mMediaRecorder.mimeType, expectedMimeType, 'blob should has mimetype, return ' + mMediaRecorder.mimeType);
+    is(e.data.type, expectedMimeType, 'blob should have expected mimetype');
+    is(mMediaRecorder.mimeType, expectedMimeType, 'recorder should have expected mimetype');
     if (!stopTriggered) {
       mMediaRecorder.stop();
       stopTriggered = true;
diff --git a/dom/media/test/test_mediarecorder_record_audionode.html b/dom/media/test/test_mediarecorder_record_audionode.html
index 731675b822a8..32c8a37a461d 100644
--- a/dom/media/test/test_mediarecorder_record_audionode.html
+++ b/dom/media/test/test_mediarecorder_record_audionode.html
@@ -65,7 +65,9 @@ async function testRecord(source, mimeType) {
 
   const chunks = [];
   let {data} = await new Promise(r => recorder.ondataavailable = r);
-  is(recorder.state, "recording", "Expected to still be recording");
+  if (!isOffline) {
+    is(recorder.state, "recording", "Expected to still be recording");
+  }
   is(data.type, recorder.mimeType, "Blob has recorder mimetype");
   if (mimeType != "") {
     is(data.type, mimeType, "Blob has given mimetype");
diff --git a/dom/media/test/test_mediarecorder_record_getdata_afterstart.html b/dom/media/test/test_mediarecorder_record_getdata_afterstart.html
index 5b7b9cabe98a..56540f2af3da 100644
--- a/dom/media/test/test_mediarecorder_record_getdata_afterstart.html
+++ b/dom/media/test/test_mediarecorder_record_getdata_afterstart.html
@@ -38,13 +38,13 @@ function startTest(test, token) {
     info('onstart fired successfully');
     hasonstart = true;
     // On audio only case, we produce audio/ogg as mimeType.
-    is('audio/ogg', mMediaRecorder.mimeType, "check the record mimetype return " + mMediaRecorder.mimeType);
+    is('audio/ogg', mMediaRecorder.mimeType, "MediaRecorder mimetype as expected");
     mMediaRecorder.requestData();
   };
 
   mMediaRecorder.onstop = function() {
     info('onstop fired successfully');
-    ok (hasondataavailable, "should have ondataavailable before onstop");
+    ok(hasondataavailable, "should have ondataavailable before onstop");
     is(mMediaRecorder.state, 'inactive', 'check recording status is inactive');
     SimpleTest.finish();
   };
@@ -53,8 +53,9 @@ function startTest(test, token) {
     info('ondataavailable fired successfully');
     if (mMediaRecorder.state == 'recording') {
       hasondataavailable = true;
-      ok(hasonstart, "should has onstart event first");
-      ok(e.data.size > 0, 'check blob has data');
+      ok(hasonstart, "should have had start event first");
+      is(e.data.type, mMediaRecorder.mimeType,
+        "blob's mimeType matches the recorder's");
       mMediaRecorder.stop();
     }
   };