Added checks to make sure the specified track exists

Added precondition checks to validate input files and paths to return more informative error messages as per #2

node_modules/jest-config/build/normalize.d.ts

@@ -0,0 +1,14 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+import { Config } from '@jest/types';
+declare type AllOptions = Config.ProjectConfig & Config.GlobalConfig;
+export default function normalize(options: Config.InitialOptions, argv: Config.Argv, configPath?: Config.Path | null, projectIndex?: number): {
+    hasDeprecationWarnings: boolean;
+    options: AllOptions;
+};
+export {};
+//# sourceMappingURL=normalize.d.ts.map