Add failure scenarios tests for connection, appendToStream, deleteStream (wip)

src/common/utils/ensure.js

@@ -8,4 +8,16 @@ module.exports.notNullOrEmpty = function(value, name) {
 module.exports.notNull = function(value, name) {
   if (value === null)
     throw new Error(name + " is null.");
+};
+
+module.exports.isInteger = function(value, name) {
+  if (typeof value !== 'number' || value % 1 !== 0)
+    throw new TypeError(name + " is not an integer.");
+};
+
+module.exports.isArrayOf = function(expectedType, value, name) {
+  if (!Array.isArray(value))
+    throw new TypeError(name + " is not an array.");
+  if (!value.every(function(x) { return x instanceof expectedType; }))
+    throw new TypeError([name, " is not an array of ", expectedType, "."].join(""));
 };