diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Device.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Device.js
index 4a1dfb63d239..426a0d6a1c15 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Device.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Device.js
@@ -35,10 +35,7 @@ function run_test() {
   var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
@@ -65,6 +62,9 @@ function run_test() {
       gfxInfo.spoofDeviceID("aabb");
       gfxInfo.spoofDriverVersion("5");
       break;
+    default:
+      do_check_true(false);
+      return;
   }
 
   createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "3", "8");
@@ -72,6 +72,7 @@ function run_test() {
 
   do_test_pending();
 
+
   function checkBlacklist() {
     var status = gfxInfo.getFeatureStatus(Ci.nsIGfxInfo.FEATURE_DIRECT2D);
     do_check_eq(status, Ci.nsIGfxInfo.FEATURE_STATUS_OK);
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_DriverNew.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_DriverNew.js
index 57457677ffa9..d0e6a3d4fe0d 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_DriverNew.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_DriverNew.js
@@ -35,10 +35,7 @@ function run_test() {
   var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
@@ -51,19 +48,16 @@ function run_test() {
       // Windows 7
       gfxInfo.spoofOSVersion(0x60001);
       break;
-    case "Linux":
-      // We don't support driver versions on Linux.
-      do_test_finished();
-      return;
-    case "Darwin":
-      // We don't support driver versions on Darwin.
-      do_test_finished();
-      return;
     case "Android":
       gfxInfo.spoofVendorID("abcd");
       gfxInfo.spoofDeviceID("wxyz");
       gfxInfo.spoofDriverVersion("6");
       break;
+    default:
+      // We don't support driver versions on Linux.
+      // We don't support driver versions on Darwin.
+      do_check_true(false);
+      return;
   }
 
   createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "3", "8");
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Equal_DriverNew.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Equal_DriverNew.js
index 8851afdcff38..713b66f6b0bc 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Equal_DriverNew.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Equal_DriverNew.js
@@ -35,10 +35,7 @@ function run_test() {
   var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
@@ -51,19 +48,16 @@ function run_test() {
       // Windows 7
       gfxInfo.spoofOSVersion(0x60001);
       break;
-    case "Linux":
-      // We don't support driver versions on Linux.
-      do_test_finished();
-      return;
-    case "Darwin":
-      // We don't support driver versions on OS X.
-      do_test_finished();
-      return;
     case "Android":
       gfxInfo.spoofVendorID("dcdc");
       gfxInfo.spoofDeviceID("uiop");
       gfxInfo.spoofDriverVersion("6");
       break;
+    default:
+      // We don't support driver versions on Linux.
+      // We don't support driver versions on OS X.
+      do_check_true(false);
+      return;
   }
 
   createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "15.0", "8");
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Equal_DriverOld.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Equal_DriverOld.js
index 1df149488bde..d07d4834b325 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Equal_DriverOld.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Equal_DriverOld.js
@@ -35,10 +35,7 @@ function run_test() {
   var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
@@ -51,19 +48,16 @@ function run_test() {
       // Windows 7
       gfxInfo.spoofOSVersion(0x60001);
       break;
-    case "Linux":
-      // We don't support driver versions on Linux.
-      do_test_finished();
-      return;
-    case "Darwin":
-      // We don't support driver versions on Darwin.
-      do_test_finished();
-      return;
     case "Android":
       gfxInfo.spoofVendorID("dcdc");
       gfxInfo.spoofDeviceID("uiop");
       gfxInfo.spoofDriverVersion("4");
       break;
+    default:
+      // We don't support driver versions on Linux.
+      // We don't support driver versions on Darwin.
+      do_check_true(false);
+      return;
   }
 
   createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "3", "8");
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Equal_OK.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Equal_OK.js
index f1dcb5b4f494..ff98ae951d8b 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Equal_OK.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Equal_OK.js
@@ -35,10 +35,7 @@ function run_test() {
   var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
@@ -51,19 +48,16 @@ function run_test() {
       // Windows 7
       gfxInfo.spoofOSVersion(0x60001);
       break;
-    case "Linux":
-      // We don't support driver versions on Linux.
-      do_test_finished();
-      return;
-    case "Darwin":
-      // We don't support driver versions on Darwin.
-      do_test_finished();
-      return;
     case "Android":
       gfxInfo.spoofVendorID("dcdc");
       gfxInfo.spoofDeviceID("uiop");
       gfxInfo.spoofDriverVersion("5");
       break;
+    default:
+      // We don't support driver versions on Linux.
+      // We don't support driver versions on Darwin.
+      do_check_true(false);
+      return;
   }
 
   createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "3", "8");
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_GTE_DriverOld.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_GTE_DriverOld.js
index 33ef972396be..972e2ae101aa 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_GTE_DriverOld.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_GTE_DriverOld.js
@@ -35,10 +35,7 @@ function run_test() {
   var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
@@ -51,19 +48,16 @@ function run_test() {
       // Windows 7
       gfxInfo.spoofOSVersion(0x60001);
       break;
-    case "Linux":
-      // We don't support driver versions on Linux.
-      do_test_finished();
-      return;
-    case "Darwin":
-      // We don't support driver versions on Darwin.
-      do_test_finished();
-      return;
     case "Android":
       gfxInfo.spoofVendorID("abab");
       gfxInfo.spoofDeviceID("ghjk");
       gfxInfo.spoofDriverVersion("6");
       break;
+    default:
+      // We don't support driver versions on Linux.
+      // We don't support driver versions on Darwin.
+      do_check_true(false);
+      return;
   }
 
   createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "3", "8");
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_GTE_OK.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_GTE_OK.js
index 4ace72563fb3..b094ba101a4d 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_GTE_OK.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_GTE_OK.js
@@ -35,10 +35,7 @@ function run_test() {
   var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
@@ -51,19 +48,16 @@ function run_test() {
       // Windows 7
       gfxInfo.spoofOSVersion(0x60001);
       break;
-    case "Linux":
-      // We don't support driver versions on Linux.
-      do_test_finished();
-      return;
-    case "Darwin":
-      // We don't support driver versions on Darwin.
-      do_test_finished();
-      return;
     case "Android":
       gfxInfo.spoofVendorID("abab");
       gfxInfo.spoofDeviceID("ghjk");
       gfxInfo.spoofDriverVersion("7");
       break;
+    default:
+      // We don't support driver versions on Linux.
+      // We don't support driver versions on Darwin.
+      do_check_true(false);
+      return;
   }
 
   createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "3", "8");
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_No_Comparison.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_No_Comparison.js
index e5093fd91ef1..daf18d2c94b8 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_No_Comparison.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_No_Comparison.js
@@ -35,10 +35,7 @@ function run_test() {
   var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OK.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OK.js
index cf3b738a7eea..bedad2532b7c 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OK.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OK.js
@@ -35,10 +35,7 @@ function run_test() {
   var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OS.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OS.js
index f8caafdde2de..e4b812b2ebc3 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OS.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OS.js
@@ -35,10 +35,7 @@ function run_test() {
   var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
@@ -51,19 +48,17 @@ function run_test() {
       // Windows Vista
       gfxInfo.spoofOSVersion(0x60000);
       break;
-    case "Linux":
-      // We don't have any OS versions on Linux, just "Linux".
-      do_test_finished();
-      return;
     case "Darwin":
       gfxInfo.spoofVendorID("0xabcd");
       gfxInfo.spoofDeviceID("0x1234");
       gfxInfo.spoofOSVersion(0x1080);
       break;
-    case "Android":
+    default:
       // On Android, the driver version is used as the OS version (because
       // there's so many of them).
-      do_test_finished();
+      //
+      // We don't have any OS versions on Linux, just "Linux".
+      do_check_true(false);
       return;
   }
 
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OSVersion_match.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OSVersion_match.js
index 0161378af8c7..c5e9d47619f9 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OSVersion_match.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OSVersion_match.js
@@ -34,10 +34,7 @@ function run_test() {
   var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
@@ -52,18 +49,16 @@ function run_test() {
       // Windows 8
       gfxInfo.spoofOSVersion(0x60002);
       break;
-    case "Linux":
-      // We don't have any OS versions on Linux, just "Linux".
-      do_test_finished();
-      return;
     case "Darwin":
       // Mountain Lion
       gfxInfo.spoofOSVersion(0x1090);
       break;
-    case "Android":
+    default:
+      // We don't have any OS versions on Linux, just "Linux".
+      //
       // On Android, the driver version is used as the OS version (because
       // there's so many of them).
-      do_test_finished();
+      do_check_true(false);
       return;
   }
 
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OSVersion_mismatch_DriverVersion.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OSVersion_mismatch_DriverVersion.js
index c8b730e1087a..c4f6651903a2 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OSVersion_mismatch_DriverVersion.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OSVersion_mismatch_DriverVersion.js
@@ -35,10 +35,7 @@ function run_test() {
   var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
@@ -53,17 +50,15 @@ function run_test() {
       // Windows 8
       gfxInfo.spoofOSVersion(0x60002);
       break;
-    case "Linux":
-      // We don't have any OS versions on Linux, just "Linux".
-      do_test_finished();
-      return;
     case "Darwin":
       gfxInfo.spoofOSVersion(0x1080);
       break;
-    case "Android":
+    default:
+      // We don't have any OS versions on Linux, just "Linux".
+      //
       // On Android, the driver version is used as the OS version (because
       // there's so many of them).
-      do_test_finished();
+      do_check_true(false);
       return;
   }
 
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OSVersion_mismatch_OSVersion.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OSVersion_mismatch_OSVersion.js
index 918efe813f0b..33935c2ca2e5 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OSVersion_mismatch_OSVersion.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_OSVersion_mismatch_OSVersion.js
@@ -35,10 +35,7 @@ function run_test() {
   var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
@@ -53,18 +50,16 @@ function run_test() {
       // Windows 7
       gfxInfo.spoofOSVersion(0x60001);
       break;
-    case "Linux":
-      // We don't have any OS versions on Linux, just "Linux".
-      do_test_finished();
-      return;
     case "Darwin":
       // Lion
       gfxInfo.spoofOSVersion(0x1080);
       break;
-    case "Android":
+    default:
+      // We don't have any OS versions on Linux, just "Linux".
+      //
       // On Android, the driver version is used as the OS version (because
       // there's so many of them).
-      do_test_finished();
+      do_check_true(false);
       return;
   }
 
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Vendor.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Vendor.js
index 901c2e17a25c..335e5db8d3e7 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Vendor.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Vendor.js
@@ -35,10 +35,7 @@ function run_test() {
   var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
@@ -65,6 +62,9 @@ function run_test() {
       gfxInfo.spoofDeviceID("asdf");
       gfxInfo.spoofDriverVersion("5");
       break;
+    default:
+      do_check_true(false);
+      return;
   }
 
   createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "3", "8");
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Version.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Version.js
index d2dd417332c7..29757fc3f0fb 100755
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Version.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_Version.js
@@ -34,10 +34,7 @@ function run_test() {
   var gfxInfo = Cc["@mozilla.org/gfx/info;1"].getService(Ci.nsIGfxInfo);
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
@@ -64,6 +61,9 @@ function run_test() {
       gfxInfo.spoofDeviceID("asdf");
       gfxInfo.spoofDriverVersion("5");
       break;
+    default:
+      do_check_true(false);
+      return;
   }
 
   createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "15.0", "8");
diff --git a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_prefs.js b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_prefs.js
index 27439f0469c7..a8aa3631e258 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_prefs.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_gfxBlacklist_prefs.js
@@ -40,10 +40,7 @@ function run_test() {
   }
 
   // We can't do anything if we can't spoof the stuff we need.
-  if (!(gfxInfo instanceof Ci.nsIGfxInfoDebug)) {
-    do_test_finished();
-    return;
-  }
+  do_check_true(gfxInfo instanceof Ci.nsIGfxInfoDebug);
 
   gfxInfo.QueryInterface(Ci.nsIGfxInfoDebug);
 
@@ -70,6 +67,9 @@ function run_test() {
       gfxInfo.spoofDeviceID("asdf");
       gfxInfo.spoofDriverVersion("5");
       break;
+    default:
+      do_check_true(false);
+      return;
   }
 
   createAppInfo("xpcshell@tests.mozilla.org", "XPCShell", "3", "8");
diff --git a/toolkit/mozapps/extensions/test/xpcshell/xpcshell-shared.ini b/toolkit/mozapps/extensions/test/xpcshell/xpcshell-shared.ini
index 6dba4285591d..3264157b55d3 100644
--- a/toolkit/mozapps/extensions/test/xpcshell/xpcshell-shared.ini
+++ b/toolkit/mozapps/extensions/test/xpcshell/xpcshell-shared.ini
@@ -194,40 +194,61 @@ skip-if = os == "android"
 [test_fuel.js]
 [test_general.js]
 [test_getresource.js]
+
+# All the following failures are expected -- certain platforms don't have the
+# concepts these tests check for. We fail so that if a new platform is added,
+# it won't silently pass these tests without auditing.
 [test_gfxBlacklist_Device.js]
+fail-if = !debug
 tags = blocklist
 [test_gfxBlacklist_DriverNew.js]
+fail-if = !debug || os == "mac" || os == "linux"
 tags = blocklist
 [test_gfxBlacklist_Equal_DriverNew.js]
+fail-if = !debug || os == "mac" || os == "linux"
 tags = blocklist
 [test_gfxBlacklist_Equal_DriverOld.js]
+fail-if = !debug || os == "mac" || os == "linux"
 tags = blocklist
 [test_gfxBlacklist_Equal_OK.js]
+fail-if = !debug || os == "mac" || os == "linux"
 tags = blocklist
 [test_gfxBlacklist_GTE_DriverOld.js]
+fail-if = !debug || os == "mac" || os == "linux"
 tags = blocklist
 [test_gfxBlacklist_GTE_OK.js]
+fail-if = !debug || os == "mac" || os == "linux"
 tags = blocklist
 [test_gfxBlacklist_No_Comparison.js]
+fail-if = !debug
 tags = blocklist
 [test_gfxBlacklist_OK.js]
+fail-if = !debug
 tags = blocklist
 [test_gfxBlacklist_OS.js]
+fail-if = !debug || os == "android" || os == "linux"
 tags = blocklist
 [test_gfxBlacklist_OSVersion_match.js]
+fail-if = !debug || os == "android" || os == "linux"
 tags = blocklist
 [test_gfxBlacklist_OSVersion_mismatch_OSVersion.js]
+fail-if = !debug || os == "android" || os == "linux"
 tags = blocklist
 [test_gfxBlacklist_OSVersion_mismatch_DriverVersion.js]
+fail-if = !debug || os == "android" || os == "linux"
 tags = blocklist
 [test_gfxBlacklist_Vendor.js]
+fail-if = !debug
 tags = blocklist
 [test_gfxBlacklist_Version.js]
+fail-if = !debug
 tags = blocklist
 [test_gfxBlacklist_prefs.js]
+fail-if = !debug
 # Bug 1248787 - consistently fails
 skip-if = true
 tags = blocklist
+
 [test_hasbinarycomponents.js]
 [test_hotfix.js]
 [test_install.js]