Warn that a failed NaN test may not be an error

Sprintf returns "-nan" rather than "nan" on some platforms, which causes
the test script to incorrectly flag a failure.

Also allow test functions without "==> Config" output.

1 files changed, 3 insertions, 1 deletions

diff --git a/tests/common.lua b/tests/common.lua
index 156f882..47e3f56 100644
--- a/tests/common.lua
+++ b/tests/common.lua
@@ -231,7 +231,9 @@ end
 function run_test_group(testgroup, tests)
     local function run_config(configname, func)
         local success, msg = pcall(func)
-        print(string.format("==> Config %s: %s", configname, msg))
+        if msg then
+            print(string.format("==> Config %s: %s", configname, msg))
+        end
         print()
     end