diff --git a/run_tests.py b/run_tests.py
index 7069b99..cc26745 100644
--- a/run_tests.py
+++ b/run_tests.py
@@ -4,21 +4,24 @@ from os.path import splitext
 import subprocess as sp
 
 COMPILER = "c++"
-# -Wno-missing-braces because clang false positive
-CXXFLAGS="-std=c++11 -Wall -Wextra -Wno-missing-braces -I."
+CXXFLAGS = [
+    "-std=c++11",
+    "-Wall", "-Wextra",
+    "-Wno-missing-braces", # clang false positive
+    "-I."
+]
 
 nsuccess = 0
 nfailed  = 0
 
-for fname in listdir("./tests"):
+for fname in listdir("tests"):
     (modname, modext) = splitext(fname)
 
     if modext != ".cpp":
         continue
 
-    pc = sp.Popen("%s tests/%s -o tests/%s %s"
-        % (COMPILER, fname, modname, CXXFLAGS), shell = True,
-            stdout = sp.PIPE, stderr = sp.STDOUT)
+    pc = sp.Popen([ COMPILER, "tests/%s" % fname, "-o", "tests/%s" % modname ]
+        + CXXFLAGS, stdout = sp.PIPE, stderr = sp.STDOUT)
     stdout.write(pc.communicate()[0])
 
     if pc.returncode != 0:
@@ -26,20 +29,19 @@ for fname in listdir("./tests"):
         nfailed += 1
         continue
 
-    pc = sp.Popen("./tests/%s" % modname, shell = True,
-        stdout = sp.PIPE, stderr = sp.STDOUT)
+    pc = sp.Popen("tests/%s" % modname, stdout = sp.PIPE, stderr = sp.STDOUT)
     stdout.write(pc.communicate()[0])
 
     if pc.returncode != 0:
-        remove("./tests/%s" % modname)
+        remove("tests/%s" % modname)
         print "%s...\t\033[91m\033[1m(runtime error)\033[0m" % modname
         nfailed += 1
         continue
 
-    remove("./tests/%s" % modname)
+    remove("tests/%s" % modname)
     print "%s...\t\033[92m\033[1m(success)\033[0m" % modname
     nsuccess += 1
 
 print "\n\033[94m\033[1mtesting done:\033[0m"
-print "\033[92mSUCCESS\033[0m: %d" % nsuccess
-print "\033[91mFAILURE\033[0m: %d" % nfailed
\ No newline at end of file
+print "\033[92mSUCCESS\033[0m: \033[1m%d\033[0m" % nsuccess
+print "\033[91mFAILURE\033[0m: \033[1m%d\033[0m" % nfailed
\ No newline at end of file