diff --git a/testing/pa/dummy/verify b/testing/pa/dummy/verify
index b1337fc..2ade374 100755
--- a/testing/pa/dummy/verify
+++ b/testing/pa/dummy/verify
@@ -4,12 +4,35 @@ input_file=$1
 output_file=$2
 ref_file=$3
 
+# validate output file
+if [ -z $output_file ]; 
+then
+    echo "output filename not given"
+    exit 1
+elif [ ! -f $output_file ]; 
+then
+    echo "output file '$output_file' is missing"
+    exit 1
+fi
+
+# validate reference file 
+if [ -z $ref_file ]; 
+then
+    echo "reference filename not given"
+    exit 1
+elif [ ! -f $ref_file ]; 
+then 
+    echo "reference file '$ref_file' is missing"
+    exit 1
+fi
+
 out_value=`head -n 1 $output_file`
 ref_value=`head -n 1 $ref_file`
+
 if [ $out_value -eq $ref_value ]; 
 then
-    exit 0; 
+    exit 0
 else
-    echo "incorrect result - expecting $ref_value, found $out_value";
-    exit 1; 
+    echo "incorrect result - expecting $ref_value, found $out_value"
+    exit 1
 fi
diff --git a/testing/pa/pa-linux_vmchecker_run.sh b/testing/pa/pa-linux_vmchecker_run.sh
index b14614e..34b9f9e 100755
--- a/testing/pa/pa-linux_vmchecker_run.sh
+++ b/testing/pa/pa-linux_vmchecker_run.sh
@@ -1,20 +1,21 @@
 #!/bin/sh
 
 # @author claudiugh 
-# Script generic de rulare a temelor sub limita de timp 
-# depinde de:
-# - tracker: trebuie sa fie compilat din Makefile.checker 
-# - verify: executabil generic (script sh/bash/python sau executabil) care verifica outputul studentului 
+# Generic script for running assignments with CPU time limit 
+# depends on:
+# - tracker: has to be compiled from Makefile.checker 
+# - verify: runnable file (sh/bash/python script or executable)
+#           verifies the ouput generated by student's assignment 
 #
 
-#home=$1
-#cd $home
+home=$1
+cd $home
 
 INPUT_DIR=input
 OUTPUT_DIR=output
 REFERENCES_DIR=refs
-TRACKER=tracker
-VERIFIER=verify
+TRACKER=./tracker
+VERIFIER=./verify
 
 print_fail_reason() 
 {
@@ -27,40 +28,40 @@ run_test()
     # run test 
     if [ -f $TRACKER ]; 
     then 
-	./$TRACKER $timeout $INPUT_DIR/$input_file $OUTPUT_DIR/$output_file \
-	    > $test_name-tracker.out 2> $test_name-tracker.err; 
-	err=$?;
-	if [ $err -eq 0 ];
-	then
-	    if [ -f $VERIFIER ]; 
-	    then
-		./$VERIFIER $INPUT_DIR/$input_file \
-		    $OUTPUT_DIR/$output_file \
-		    $REFERENCES_DIR/$output_file \
-		    > $test_name-verifier.out
-		if [ $? -eq 0 ]; 
-		then
-		    echo $test_name: passed; 
-		    echo `cat $test_name-tracker.out`;
-		    return 0; 
-		else
-		    echo $test_name: failed; 
-		    echo reason: `cat $test_name-verifier.out`; 
-		    return 1; 
-		fi
-	    else
-		echo "verifier not found";
-		exit; 
-	    fi
-	else
-	    echo $test_name: failed;
-	    print_fail_reason; 
-	    return 1; 
-	    echo; 
-	fi
+        $TRACKER $timeout $INPUT_DIR/$input_file $OUTPUT_DIR/$output_file \
+            > $test_name-tracker.out 2> $test_name-tracker.err; 
+        err=$?;
+        if [ $err -eq 0 ];
+        then
+            if [ -f $VERIFIER ]; 
+            then
+                $VERIFIER $INPUT_DIR/$input_file \
+                    $OUTPUT_DIR/$output_file \
+                    $REFERENCES_DIR/$output_file \
+                    > $test_name-verifier.out
+                if [ $? -eq 0 ]; 
+                then
+                    echo $test_name: passed; 
+                    echo `cat $test_name-tracker.out`;
+                    return 0; 
+                else
+                    echo $test_name: failed; 
+                    echo reason: `cat $test_name-verifier.out`; 
+                    return 1; 
+                fi
+            else
+                echo "verifier not found";
+                exit; 
+            fi
+        else
+            echo $test_name: failed;
+            print_fail_reason; 
+            return 1; 
+            echo; 
+        fi
     else 
-	echo "the tracker is not built"; 
-	exit; 
+        echo "the tracker is not built"; 
+        exit; 
     fi  
 }
 
@@ -73,16 +74,16 @@ run_all_tests()
     failed=0
     for input_file in $input_files
     do
-	test_name=`echo $input_file | sed s/\.in//`
-	output_file=$test_name.out
-	run_test
-	if [ $? -eq 0 ];
-	then
-	    passed=`expr $passed + 1` 
-	else
-	    failed=`expr $failed + 1`
-	fi
-	echo; 
+        test_name=`echo $input_file | sed s/\.in//`
+        output_file=$test_name.out
+        run_test
+        if [ $? -eq 0 ];
+        then
+            passed=`expr $passed + 1` 
+        else
+            failed=`expr $failed + 1`
+        fi
+        echo; 
     done
     echo; echo results: $passed passed, $failed failed; 
 }
@@ -93,11 +94,11 @@ detect_lang()
     java_files=`ls | grep -c .java$`
     if [ $java_files -gt 0 ]; 
     then 
-	echo "language: java"
-	lang="java"
+        echo "language: java"
+        lang="java"
     else 
-	echo "language: c/c++";
-	lang="c"
+        echo "language: c/c++";
+        lang="c"
     fi
 }
 
@@ -105,7 +106,7 @@ setup()
 {
     if [ ! -d $OUTPUT_DIR ]; 
     then
-	mkdir $OUTPUT_DIR
+        mkdir $OUTPUT_DIR
     fi
 }