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/transform/build/ScriptTransformer.d.ts

@@ -0,0 +1,36 @@
+/**
+ * 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 { Options, TransformResult } from './types';
+export default class ScriptTransformer {
+    static EVAL_RESULT_VARIABLE: 'Object.<anonymous>';
+    private _cache;
+    private _config;
+    private _transformCache;
+    constructor(config: Config.ProjectConfig);
+    private _getCacheKey;
+    private _getFileCachePath;
+    private _getTransformPath;
+    private _getTransformer;
+    private _instrumentFile;
+    private _getRealPath;
+    preloadTransformer(filepath: Config.Path): void;
+    transformSource(filepath: Config.Path, content: string, instrument: boolean): {
+        code: string;
+        mapCoverage: boolean;
+        sourceMapPath: string | null;
+    };
+    private _transformAndBuildScript;
+    transform(filename: Config.Path, options: Options, fileSource?: string): TransformResult;
+    transformJson(filename: Config.Path, options: Options, fileSource: string): string;
+    /**
+     * @deprecated use `this.shouldTransform` instead
+     */
+    private _shouldTransform;
+    shouldTransform(filename: Config.Path): boolean;
+}
+//# sourceMappingURL=ScriptTransformer.d.ts.map