tests: Improve result handling in cpuTestGuestData()

A test is considered successful if the obtained result matches
the expected result: if that's not the case, whether because a
test that was expected to succeed failed or because a test that
was supposed to fail succeeded, then something's not right and
we want the user to know about this.

On the other hand, if a failure that's unrelated to the bits
we're testing occurs, then the user should be notified even if
the test was expected to fail.

Use different values to tell these two situations apart.

Fix a test case that was wrongly expected to fail as well.

tests/cputest.c

@@ -247,7 +247,7 @@ static int
 cpuTestGuestData(const void *arg)
 {
     const struct data *data = arg;
-    int ret = -1;
+    int ret = -2;
     virCPUDefPtr host = NULL;
     virCPUDefPtr cpu = NULL;
     virCPUDefPtr guest = NULL;
@@ -262,8 +262,10 @@ cpuTestGuestData(const void *arg)
 
     cmpResult = cpuGuestData(host, cpu, &guestData, NULL);
     if (cmpResult == VIR_CPU_COMPARE_ERROR ||
-        cmpResult == VIR_CPU_COMPARE_INCOMPATIBLE)
+        cmpResult == VIR_CPU_COMPARE_INCOMPATIBLE) {
+        ret = -1;
         goto cleanup;
+    }
 
     if (VIR_ALLOC(guest) < 0)
         goto cleanup;
@@ -274,10 +276,7 @@ cpuTestGuestData(const void *arg)
     guest->fallback = cpu->fallback;
     if (cpuDecode(guest, guestData, data->models,
                   data->nmodels, data->preferred) < 0) {
-        if (data->result < 0) {
-            virResetLastError();
-            ret = 0;
-        }
+        ret = -1;
         goto cleanup;
     }
 
@@ -294,7 +293,10 @@ cpuTestGuestData(const void *arg)
     }
     result = virBufferContentAndReset(&buf);
 
-    ret = cpuTestCompareXML(data->arch, guest, result, false);
+    if (cpuTestCompareXML(data->arch, guest, result, false) < 0)
+        goto cleanup;
+
+    ret = 0;
 
  cleanup:
     VIR_FREE(result);
@@ -302,6 +304,20 @@ cpuTestGuestData(const void *arg)
     virCPUDefFree(host);
     virCPUDefFree(cpu);
     virCPUDefFree(guest);
+
+    if (ret == data->result) {
+        /* We got the result we expected, whether it was
+         * a success or a failure */
+        virResetLastError();
+        ret = 0;
+    } else {
+        VIR_TEST_VERBOSE("\nExpected result %d, got %d\n",
+                         data->result, ret);
+        /* Pad to line up with test name ... in virTestRun */
+        VIR_TEST_VERBOSE("%74s", "... ");
+        ret = -1;
+    }
+
     return ret;
 }
 
@@ -646,7 +662,7 @@ mymain(void)
                       NULL, "Haswell-noTSX", 0);
 
     DO_TEST_GUESTDATA("ppc64", "host", "guest", ppc_models, NULL, 0);
-    DO_TEST_GUESTDATA("ppc64", "host", "guest-nofallback", ppc_models, "POWER7_v2.1", -1);
+    DO_TEST_GUESTDATA("ppc64", "host", "guest-nofallback", ppc_models, "POWER7_v2.1", 0);
 
     return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }