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-runner/build/testWorker.d.ts

@@ -0,0 +1,27 @@
+/**
+ * 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';
+import { TestResult } from '@jest/test-result';
+import { SerializableModuleMap } from 'jest-haste-map';
+import { TestRunnerSerializedContext } from './types';
+export declare type SerializableResolver = {
+    config: Config.ProjectConfig;
+    serializableModuleMap: SerializableModuleMap;
+};
+declare type WorkerData = {
+    config: Config.ProjectConfig;
+    globalConfig: Config.GlobalConfig;
+    path: Config.Path;
+    context?: TestRunnerSerializedContext;
+};
+export declare function setup(setupData: {
+    serializableResolvers: Array<SerializableResolver>;
+}): void;
+export declare function worker({ config, globalConfig, path, context, }: WorkerData): Promise<TestResult>;
+export {};
+//# sourceMappingURL=testWorker.d.ts.map