correct typo, mention Therac-25

Author: alessandrofelder

ch03tests/01testingbasics.ipynb

@@ -76,11 +76,18 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    " * Testing won't corrrect a buggy code\n",
+    " * Testing won't correct a buggy code\n",
     " * Testing will tell you were the bugs are...\n",
     " * ... if the test cases *cover* the bugs"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "If the test cases do not cover the bugs, things can go horribly wrong - an example for this is [Therac-25](https://en.wikipedia.org/wiki/Therac-25)."
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},