COMPMID-582: Add validation to channel_extract kernels.

Change-Id: I6413a05f6870a0d04f12d7348269b15297ae8493
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/114696
Tested-by: Jenkins <bsgcomp@arm.com>
Reviewed-by: Anthony Barbier <anthony.barbier@arm.com>
diff --git a/tests/SimpleTensor.h b/tests/SimpleTensor.h
index 902f5b5..f3155ff 100644
--- a/tests/SimpleTensor.h
+++ b/tests/SimpleTensor.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2018 ARM Limited.
+ * Copyright (c) 2017-2018 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -297,18 +297,33 @@
     switch(_format)
     {
         case Format::U8:
-        case Format::S16:
         case Format::U16:
-        case Format::S32:
+        case Format::S16:
         case Format::U32:
+        case Format::S32:
+        case Format::F16:
         case Format::F32:
             return 1;
+        // Because the U and V channels are subsampled
+        // these formats appear like having only 2 channels:
+        case Format::YUYV422:
+        case Format::UYVY422:
+            return 2;
+        case Format::UV88:
+            return 2;
         case Format::RGB888:
             return 3;
+        case Format::RGBA8888:
+            return 4;
         case Format::UNKNOWN:
             return _num_channels;
+        //Doesn't make sense for planar formats:
+        case Format::NV12:
+        case Format::NV21:
+        case Format::IYUV:
+        case Format::YUV444:
         default:
-            ARM_COMPUTE_ERROR("NOT SUPPORTED!");
+            return 0;
     }
 }