tests: qemublock: Add tests for basic backing chain formats

Formats supporting backing chain such as qed, vmdk, don't have any other
parameters than the backing store and 'qcow' has only encryption params
which will be tested extra. Add this test case so they are covered since
any further test cases will mainly care about 'qcow2' and 'raw'.

The top level disk image would generate the following '-drive' cmdline:

-drive file=/var/lib/libvirt/images/a,format=qed,if=none,id=drive-dummy
-device virtio-blk-pci,scsi=off,drive=drive-dummy,id=dummy
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>

tests/qemublocktest.c

@@ -414,6 +414,8 @@ mymain(void)
     TEST_DISK_TO_JSON("file-vhd-noopts");
     TEST_DISK_TO_JSON("file-vpc-noopts");
 
+    TEST_DISK_TO_JSON("file-backing_basic-noopts");
+
  cleanup:
     virHashFree(diskxmljsondata.schema);
     qemuTestDriverFree(&driver);

tests/qemublocktestdata/xml2json/file-backing_basic-noopts.json

+{
+  "node-name": "node-a-f",
+  "read-only": false,
+  "driver": "qed",
+  "file": {
+    "driver": "file",
+    "filename": "/var/lib/libvirt/images/a",
+    "node-name": "node-a-s",
+    "read-only": false,
+    "discard": "unmap"
+  },
+  "backing": "node-b-f"
+}
+{
+  "node-name": "node-b-f",
+  "read-only": true,
+  "driver": "qcow",
+  "file": {
+    "driver": "file",
+    "filename": "/var/lib/libvirt/images/b",
+    "node-name": "node-b-s",
+    "read-only": true,
+    "discard": "unmap"
+  },
+  "backing": "node-c-f"
+}
+{
+  "node-name": "node-c-f",
+  "read-only": true,
+  "driver": "vmdk",
+  "file": {
+    "driver": "file",
+    "filename": "/var/lib/libvirt/images/c",
+    "node-name": "node-c-s",
+    "read-only": true,
+    "discard": "unmap"
+  },
+  "backing": "node-d-f"
+}
+{
+  "node-name": "node-d-f",
+  "read-only": true,
+  "driver": "raw",
+  "file": {
+    "driver": "file",
+    "filename": "/var/lib/libvirt/images/d",
+    "node-name": "node-d-s",
+    "read-only": true,
+    "discard": "unmap"
+  }
+}

tests/qemublocktestdata/xml2json/file-backing_basic-noopts.xml

+<disk type='file' device='disk'>
+  <driver name='qemu' type='qed'/>
+  <source file='/var/lib/libvirt/images/a'>
+    <privateData>
+      <nodenames>
+        <nodename type='storage' name='node-a-s'/>
+        <nodename type='format' name='node-a-f'/>
+      </nodenames>
+    </privateData>
+  </source>
+  <backingStore type='file' index='1'>
+    <format type='qcow'/>
+    <source file='/var/lib/libvirt/images/b'>
+      <privateData>
+        <nodenames>
+          <nodename type='storage' name='node-b-s'/>
+          <nodename type='format' name='node-b-f'/>
+        </nodenames>
+      </privateData>
+    </source>
+    <backingStore type='file' index='2'>
+      <format type='vmdk'/>
+      <source file='/var/lib/libvirt/images/c'>
+        <privateData>
+          <nodenames>
+            <nodename type='storage' name='node-c-s'/>
+            <nodename type='format' name='node-c-f'/>
+          </nodenames>
+        </privateData>
+      </source>
+      <backingStore type='file' index='3'>
+        <format type='raw'/>
+        <source file='/var/lib/libvirt/images/d'>
+          <privateData>
+            <nodenames>
+              <nodename type='storage' name='node-d-s'/>
+              <nodename type='format' name='node-d-f'/>
+            </nodenames>
+          </privateData>
+        </source>
+        <backingStore/>
+      </backingStore>
+    </backingStore>
+  </backingStore>
+  <target dev='vda'/>
+</disk>