diff --git a/include/db.php b/include/db.php
index a3c2997..ee68963 100644
--- a/include/db.php
+++ b/include/db.php
@@ -50,10 +50,14 @@ function query_parameters()
 
     $data = func_get_args();
     $query = $data[0];
-    $tokens = split("[\&\?\~]", $query);
+    $tokens = split("[&?~]", $query); /* NOTE: no need to escape characters inside of [] in regex */
     $preparedquery = $tokens[0];
     $count = strlen($tokens[0]);
 
+    /* do we have the correct number of tokens to the number of parameters provided? */
+    if(count($tokens) != count($data))
+        return NULL; /* count mismatch, return NULL */
+
     for ($i=1; $i < count($tokens); $i++)
     {
         $char = substr($query, $count, 1);
diff --git a/unit_test/run_tests.php b/unit_test/run_tests.php
index 0163edf..14bedfb 100644
--- a/unit_test/run_tests.php
+++ b/unit_test/run_tests.php
@@ -6,6 +6,8 @@
 /* TODO: test the rest of the classes we have */
 
 include_once("test_user.php");
+echo "\n";
+include_once("test_db.php");
 
 
 ?>
\ No newline at end of file
diff --git a/unit_test/test_common.php b/unit_test/test_common.php
new file mode 100644
index 0000000..2cb34b1
--- /dev/null
+++ b/unit_test/test_common.php
@@ -0,0 +1,10 @@
+<?php
+
+/* common functions used in appdb unit tests */
+
+function test_start($sFunctionName)
+{
+    echo $sFunctionName."() starting\n";
+}
+
+?>
\ No newline at end of file
diff --git a/unit_test/test_db.php b/unit_test/test_db.php
new file mode 100644
index 0000000..7b7574d
--- /dev/null
+++ b/unit_test/test_db.php
@@ -0,0 +1,127 @@
+<?php
+
+/* unit tests for functions in include/db.php */
+
+require_once("path.php");
+require_once("test_common.php");
+
+/* test query_parameters() */
+/* query_parameters() is key to protecting sql queries from injection attacks */
+/* while also being simple and easy to use */
+function test_query_parameters()
+{
+    test_start(__FUNCTION__);
+
+    /* see that queries without parameters work properly */
+    $sQuery = "SELECT count(*) as count from user_list";
+    $hResult = query_parameters($sQuery);
+    if(!$hResult)
+    {
+        echo "sQuery of '".$sQuery."' failed but should have succeeded\n";
+        return false;
+    }
+
+    /* see that '?' marks in queries are replaced with parameters */
+    $sQuery = "SELECT count(*) as count from ?";
+    $hResult = query_parameters($sQuery, "user_list");
+    if(!$hResult)
+    {
+        echo "sQuery of '".$sQuery."' failed but should have succeeded\n";
+        return false;
+    }
+
+    $oRow = mysql_fetch_object($hResult);
+    $iUserCount = $oRow->count;
+
+    /* see that '~' strings are replaced with parameters */
+    /* NOTE: if the second parameter is quoted this query will produce */
+    /*  a different number of results than if it was */
+    /* NOTE: The second parameter is an example of a SQL injection attack */
+    $sQuery = "SELECT count(*) as count from ~ where userid='~'";
+    $hResult = query_parameters($sQuery, "user_list", "1' OR 1='1");
+    if($hResult)
+    {
+        $oRow = mysql_fetch_object($hResult);
+        if($iUserCount != $oRow->count)
+        {
+            echo "sQuery of '".$sQuery."' returned ".$oRow->count." entries instead of the expected ".$iUserCount."\n";
+            return false;
+        }
+
+        if($iUserCount == 0)
+        {
+            echo "Because iUserCount is zero we can't know if this test passed or failed\n";
+        }
+    } else
+    {
+        echo "sQuery of '".$sQuery."' failed but should have succeeded\n";
+        return false;
+    }
+
+    /**
+     * test that '&' in a query is properly replaced by the contents from a file
+     */
+    /* write to a file that we will use for the test of '&' */
+    $sFilename = "/tmp/test_db.txt";
+    $hFile = fopen($sFilename, "wb");
+    if($hFile)
+    {
+        fwrite($hFile, "user_list");
+        fclose($hFile);
+
+        $sQuery = "SELECT count(*) as count from &";
+        $hResult = query_parameters($sQuery, $sFilename);
+        unlink($sFilename); /* delete the temporary file we've created */
+        if(!$hResult)
+        {
+            echo "sQuery of '".$sQuery."' failed but should have succeeded\n";
+            return false;
+        }
+    } else
+    {
+        echo "Could not open '".$sFilename."' for writing to complete the '&' test\n";
+    }
+  
+    /**
+     * test that queries with slashes in them are parameterized properly
+     * NOTE: this test exists because query_parameters() at one point did not work
+     *       properly with slashes in the query, they were incorrectly being recognized
+     *       as tokens that should be replaced with parameters
+     */
+    $sQuery = "SELECT count(*) as count, '".mysql_real_escape_string("\r\n")."' as x from ?";
+    $hResult = query_parameters($sQuery, "user_list");
+    if(!$hResult)
+    {
+        echo "sQuery of '".$sQuery."' failed but should have succeeded\n";
+        return false;
+    }
+
+    /* test that queries with too many parameters are rejected */
+    $sQuery = "SELECT count(*) as count from ?";
+    $hResult = query_parameters($sQuery, "user_list", "12");
+    if($hResult)
+    {
+        echo "sQuery of '".$sQuery."' succeeded but should have failed for too many parameters\n";
+        return false;
+    }
+
+    /* test that queries with too few parameters are rejected */
+    $sQuery = "SELECT count(*) as count from ?";
+    $hResult = query_parameters($sQuery);
+    if($hResult)
+    {
+        echo "sQuery of '".$sQuery."' succeeded but should have failed for too few parameters\n";
+        return false;
+    }
+
+    return true;
+}
+
+
+if(!test_query_parameters())
+    echo "test_query_parameters() failed!\n";
+else
+    echo "test_query_parameters() passed!\n";
+
+
+?>
\ No newline at end of file
diff --git a/unit_test/test_user.php b/unit_test/test_user.php
index 29bcd92..f40b08a 100644
--- a/unit_test/test_user.php
+++ b/unit_test/test_user.php
@@ -3,6 +3,7 @@
 /* unit tests for user class */
 
 require_once("path.php");
+require_once("test_common.php");
 require_once(BASE."include/incl.php");
 require_once(BASE."include/user.php");
 
@@ -11,11 +12,6 @@ require_once(BASE."include/user.php");
 $test_email = "testemail@somesite.com";
 $test_password = "password";
 
-function test_start($sFunctionName)
-{
-    echo $sFunctionName."() starting\n";
-}
-
 /* NOTE: test_user_login() relies on this function leaving the test user */
 /* in the database */
 function test_user_create()