[RFC PATCH 09/41] qemublocktest: Add 'empty' case for incremental backup test

[Peter Krempa <pkrempa@xxxxxxxxxx>]

Use the new test data when calculating incremental backup operations. As
incremental backup fails with no bitmap the test code is modified to
allow testing this case too.

Signed-off-by: Peter Krempa <pkrempa@xxxxxxxxxx>
---
 tests/qemublocktest.c                         | 19 ++++++++++---------
 .../backupmerge/empty-out.json                |  1 +
 2 files changed, 11 insertions(+), 9 deletions(-)
 create mode 100644 tests/qemublocktestdata/backupmerge/empty-out.json

diff --git a/tests/qemublocktest.c b/tests/qemublocktest.c
index 8d613d7cac..9e54c254e8 100644
--- a/tests/qemublocktest.c
+++ b/tests/qemublocktest.c
@@ -793,17 +793,16 @@ testQemuBackupIncrementalBitmapCalculate(const void *opaque)

     incremental = testQemuBackupGetIncremental(data->incremental);

-    if (!(mergebitmaps = qemuBackupDiskPrepareOneBitmapsChain(incremental,
-                                                              data->chain,
-                                                              nodedata,
-                                                              "testdisk"))) {
-        VIR_TEST_VERBOSE("failed to calculate merged bitmaps");
-        return -1;
+    if ((mergebitmaps = qemuBackupDiskPrepareOneBitmapsChain(incremental,
+                                                             data->chain,
+                                                             nodedata,
+                                                             "testdisk"))) {
+        if (!(actual = virJSONValueToString(mergebitmaps, true)))
+            return -1;
+    } else {
+        actual = g_strdup("NULL\n");
     }

-    if (!(actual = virJSONValueToString(mergebitmaps, true)))
-        return -1;
-
     return virTestCompareToFile(actual, expectpath);
 }

@@ -1312,6 +1311,8 @@ mymain(void)
             ret = -1; \
     } while (0)

+    TEST_BACKUP_BITMAP_CALCULATE("empty", bitmapSourceChain, "a", "empty");
+
     TEST_BACKUP_BITMAP_CALCULATE("basic-flat", bitmapSourceChain, "current", "basic");
     TEST_BACKUP_BITMAP_CALCULATE("basic-intermediate", bitmapSourceChain, "d", "basic");
     TEST_BACKUP_BITMAP_CALCULATE("basic-deep", bitmapSourceChain, "a", "basic");
diff --git a/tests/qemublocktestdata/backupmerge/empty-out.json b/tests/qemublocktestdata/backupmerge/empty-out.json
new file mode 100644
index 0000000000..7951defec1
--- /dev/null
+++ b/tests/qemublocktestdata/backupmerge/empty-out.json
@@ -0,0 +1 @@
+NULL
-- 
2.26.2