Fix a typo

Signed-off-by: Gavin Howard <gavin@yzena.com>
diff --git a/tests/history.py b/tests/history.py
index 050691b..0c7f0aa 100755
--- a/tests/history.py
+++ b/tests/history.py
@@ -1014,7 +1014,7 @@
 	print("       The valid values for dir are: 'bc' and 'dc'.")
 	print("       The max test_idx for bc is {}.".format(len(bc_tests) - 1))
 	print("       The max test_idx for dc is {}.".format(len(dc_tests) - 1))
-	print("       If -a is given, the number of test for dir is printed.")
+	print("       If -a is given, the number of tests for dir is printed.")
 	print("       No tests are run.")
 	sys.exit(1)