diff --git a/tests/qemu-iotests/017 b/tests/qemu-iotests/017
index 66951eb..d31432f 100755
--- a/tests/qemu-iotests/017
+++ b/tests/qemu-iotests/017
@@ -40,7 +40,7 @@ trap "_cleanup; exit \$status" 0 1 2 3 15
 . ./common.pattern
 
 # Any format supporting backing files
-_supported_fmt qcow qcow2 vmdk qed
+_supported_fmt qcow qcow2 vmdk qed add-cow
 _supported_proto generic
 _supported_os Linux
 
diff --git a/tests/qemu-iotests/018 b/tests/qemu-iotests/018
index bd2db78..aa7444f 100755
--- a/tests/qemu-iotests/018
+++ b/tests/qemu-iotests/018
@@ -40,7 +40,7 @@ trap "_cleanup; exit \$status" 0 1 2 3 15
 . ./common.pattern
 
 # Any format supporting backing files
-_supported_fmt qcow qcow2 vmdk qed
+_supported_fmt qcow qcow2 vmdk qed add-cow
 _supported_proto generic
 _supported_os Linux
 
diff --git a/tests/qemu-iotests/019 b/tests/qemu-iotests/019
index 8872b30..d938aca 100755
--- a/tests/qemu-iotests/019
+++ b/tests/qemu-iotests/019
@@ -44,7 +44,7 @@ trap "_cleanup; exit \$status" 0 1 2 3 15
 . ./common.pattern
 
 # Any format supporting backing files
-_supported_fmt qcow qcow2 vmdk qed
+_supported_fmt qcow qcow2 vmdk qed add-cow
 _supported_proto generic
 _supported_os Linux
 
diff --git a/tests/qemu-iotests/020 b/tests/qemu-iotests/020
index 2fb0ff8..3dbb495 100755
--- a/tests/qemu-iotests/020
+++ b/tests/qemu-iotests/020
@@ -42,7 +42,7 @@ trap "_cleanup; exit \$status" 0 1 2 3 15
 . ./common.pattern
 
 # Any format supporting backing files
-_supported_fmt qcow qcow2 vmdk qed
+_supported_fmt qcow qcow2 vmdk qed add-cow
 _supported_proto generic
 _supported_os Linux
 
diff --git a/tests/qemu-iotests/check b/tests/qemu-iotests/check
index 432732c..8061059 100755
--- a/tests/qemu-iotests/check
+++ b/tests/qemu-iotests/check
@@ -243,7 +243,7 @@ do
 		echo " - no qualified output"
 		err=true
 	    else
-		if diff -w $seq.out $tmp.out >/dev/null 2>&1
+		if diff -w -I "^Formatting" $seq.out $tmp.out >/dev/null 2>&1
 		then
 		    echo ""
 		    if $err
@@ -255,7 +255,7 @@ do
 		else
 		    echo " - output mismatch (see $seq.out.bad)"
 		    mv $tmp.out $seq.out.bad
-		    $diff -w $seq.out $seq.out.bad
+		    $diff -w -I "^Formatting" $seq.out $seq.out.bad
 		    err=true
 		fi
 	    fi
diff --git a/tests/qemu-iotests/common b/tests/qemu-iotests/common
index eeb70cb..c80d18c 100644
--- a/tests/qemu-iotests/common
+++ b/tests/qemu-iotests/common
@@ -127,6 +127,7 @@ common options
 check options
     -raw                test raw (default)
     -cow                test cow
+    -add-cow            test add-cow
     -qcow               test qcow
     -qcow2              test qcow2
     -qed                test qed
@@ -162,6 +163,11 @@ testlist options
 	    xpand=false
 	    ;;
 
+    -add-cow)
+        IMGFMT=add-cow
+        xpand=false
+       ;;
+
 	-qcow)
 	    IMGFMT=qcow
 	    xpand=false
diff --git a/tests/qemu-iotests/common.rc b/tests/qemu-iotests/common.rc
index e535874..93595c3 100644
--- a/tests/qemu-iotests/common.rc
+++ b/tests/qemu-iotests/common.rc
@@ -87,6 +87,18 @@ _make_test_img()
     fi
     if [ \( "$IMGFMT" = "qcow2" -o "$IMGFMT" = "qed" \) -a -n "$CLUSTER_SIZE" ]; then
         optstr=$(_optstr_add "$optstr" "cluster_size=$CLUSTER_SIZE")
+    elif [ "$IMGFMT" = "add-cow" ]; then
+        local BACKING="$TEST_IMG"".qcow2"
+        local IMG="$TEST_IMG"".raw"
+        if [ "$1" = "-b" ]; then
+            IMG="$IMG"".b"
+            $QEMU_IMG create -f raw $IMG $image_size>/dev/null
+            extra_img_options="-o image_file=$IMG $extra_img_options"
+        else
+            $QEMU_IMG create -f raw $IMG $image_size>/dev/null
+            $QEMU_IMG create -f qcow2 $BACKING $image_size>/dev/null
+            extra_img_options="-o backing_file=$BACKING,image_file=$IMG"
+        fi
     fi
 
     if [ -n "$optstr" ]; then
@@ -114,6 +126,13 @@ _cleanup_test_img()
             rm -f $TEST_DIR/t.$IMGFMT
             rm -f $TEST_DIR/t.$IMGFMT.orig
             rm -f $TEST_DIR/t.$IMGFMT.base
+            if [ "$IMGFMT" = "add-cow" ]; then
+                rm -f $TEST_DIR/t.$IMGFMT.qcow2
+                rm -f $TEST_DIR/t.$IMGFMT.raw
+                rm -f $TEST_DIR/t.$IMGFMT.raw.b
+                rm -f $TEST_DIR/t.$IMGFMT.ct.qcow2
+                rm -f $TEST_DIR/t.$IMGFMT.ct.raw
+            fi
             ;;
 
         rbd)
