Added 'DishError' and refined test results.

src/core/errors/DishError.mjs

@@ -0,0 +1,26 @@
+/**
+ * Custom error type for handling Dish type errors.
+ * i.e. where the Dish cannot be successfully translated between types
+ *
+ * @author n1474335 [n1474335@gmail.com]
+ * @copyright Crown Copyright 2018
+ * @license Apache-2.0
+ */
+class DishError extends Error {
+    /**
+     * Standard error constructor. Adds no new behaviour.
+     *
+     * @param args - Standard error args
+     */
+    constructor(...args) {
+        super(...args);
+
+        this.type = "DishError";
+
+        if (Error.captureStackTrace) {
+            Error.captureStackTrace(this, DishError);
+        }
+    }
+}
+
+export default DishError;