JS: Add regression tests

Author: asgerf

javascript/ql/test/query-tests/Expressions/UnneededDefensiveProgramming/UnneededDefensiveProgramming.expected

@@ -1,4 +1,6 @@
 | module-environment-detection.js:23:8:23:36 | typeof  ... efined' | This guard always evaluates to true. |
+| regression.js:9:9:9:12 | date | This guard always evaluates to true. |
+| regression.js:13:25:13:40 | obj != undefined | This guard always evaluates to true. |
 | tst2.js:4:12:4:35 | typeof  ... efined" | This guard always evaluates to true. |
 | tst.js:18:5:18:5 | u | This guard always evaluates to false. |
 | tst.js:19:5:19:5 | n | This guard always evaluates to false. |

javascript/ql/test/query-tests/Expressions/UnneededDefensiveProgramming/regression.js

@@ -0,0 +1,15 @@
+function getDate() {
+	var date;
+	if (something()) {
+		date = new Date();
+	} else {
+		return null;
+	}
+	console.log(date);
+	return date && date.getTime(); // NOT OK
+}
+
+function isNotNullOrString(obj) {
+  return obj != null && obj != undefined && // NOT OK
+      typeof obj != 'string'; 
+}