--- a/netwerk/test/unit/test_cache2-29c-concurrent_read_half-interrupted.js
+++ b/netwerk/test/unit/test_cache2-29c-concurrent_read_half-interrupted.js
@@ -55,21 +55,16 @@ function contentHandler(metadata, respon
     let len = responseBody.length;
 	  response.setHeader("Content-Range", "0-" + (len - 1) + "/" + len);
   }
   response.bodyOutputStream.write(responseBody, responseBody.length);
 }
 
 function run_test()
 {
-  if (!newCacheBackEndUsed()) {
-    do_check_true(true, "This test doesn't run when the old cache back end is used since the behavior is different");
-    return;
-  }
-
   // Static check
   do_check_true(responseBody.length > 1024);
 
   do_get_profile();
 
   Services.prefs.setIntPref("browser.cache.disk.max_entry_size", 1);
 
   httpServer = new HttpServer();

--- a/netwerk/test/unit/test_cache2-29d-concurrent_read_half-corrupted-206.js
+++ b/netwerk/test/unit/test_cache2-29d-concurrent_read_half-corrupted-206.js
@@ -60,16 +60,21 @@ function contentHandler(metadata, respon
 
 function run_test()
 {
   // Static check
   do_check_true(responseBody.length > 1024);
 
   do_get_profile();
 
+  if (!newCacheBackEndUsed()) {
+    do_check_true(true, "This test doesn't run when the old cache back end is used since the behavior is different");
+    return;
+  }
+
   Services.prefs.setIntPref("browser.cache.disk.max_entry_size", 1);
 
   httpServer = new HttpServer();
   httpServer.registerPathHandler("/content", contentHandler);
   httpServer.start(-1);
 
   var chan1 = make_channel(URL + "/content");
   chan1.asyncOpen2(new ChannelListener(firstTimeThrough, null));

--- a/netwerk/test/unit/test_cache2-29e-concurrent_read_half-non-206-response.js
+++ b/netwerk/test/unit/test_cache2-29e-concurrent_read_half-non-206-response.js
@@ -50,26 +50,26 @@ function contentHandler(metadata, respon
   response.setHeader("Cache-Control", "max-age=99999");
   response.setHeader("Accept-Ranges", "bytes");
   response.setHeader("Content-Length", "" + responseBody.length);
   response.bodyOutputStream.write(responseBody, responseBody.length);
 }
 
 function run_test()
 {
+  // Static check
+  do_check_true(responseBody.length > 1024);
+
+  do_get_profile();
+
   if (!newCacheBackEndUsed()) {
     do_check_true(true, "This test doesn't run when the old cache back end is used since the behavior is different");
     return;
   }
 
-  // Static check
-  do_check_true(responseBody.length > 1024);
-
-  do_get_profile();
-
   Services.prefs.setIntPref("browser.cache.disk.max_entry_size", 1);
 
   httpServer = new HttpServer();
   httpServer.registerPathHandler("/content", contentHandler);
   httpServer.start(-1);
 
   var chan1 = make_channel(URL + "/content");
   chan1.asyncOpen2(new ChannelListener(firstTimeThrough, null));