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-jasmine2/build/jasmine/CallTracker.d.ts

@@ -0,0 +1,26 @@
+/**
+ * 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.
+ *
+ */
+export declare type Context = {
+    object: unknown;
+    args: Array<unknown>;
+    returnValue?: unknown;
+};
+declare class CallTracker {
+    track: (context: Context) => void;
+    any: () => boolean;
+    count: () => number;
+    argsFor: (index: number) => Array<unknown>;
+    all: () => Array<Context>;
+    allArgs: () => Array<unknown>;
+    first: () => Context;
+    mostRecent: () => Context;
+    reset: () => void;
+    constructor();
+}
+export default CallTracker;
+//# sourceMappingURL=CallTracker.d.ts.map