/**  * Each year, Santa receives wish lists coming from everywhere.  *  * Lists are ordered starting by the most important present to the last  * important one. Santa does not always offer the most important one.  * From time to time he wants to wait one more year to check if the  * present stays in the top.  *  * Each year, Santa manually performs a diff of the list with  * the one of the year before. Based on this diff he makes his choice.  *  * You can see the diff manually computed by Santa as an usual git diff  * between two strings including many lines.  *  * Let's take the example:  *  *   Year N:  *     Cars  *     Trains  *     Planes  *  *   Year N+1:  *     Cars  *     Buses  *     Trains  *     Boats  *  *   Diff of Santa:  *     === Cars  *     +++ Buses  *     === Trains  *     +++ Boats  *     --- Planes  *  * @param before - String representing the list of presents (before)  * @param after - String representing the list of presents (after)  */ declare function wishListsDiffer(before: string, after: string): string; 

it("should compute the appropriate diff", () => {   // Arrange   const previousYear = "Cars
Trains
Planes";   const currentYear = "Cars
Buses
Trains
Boats";    // Act   const diff = wishListsDiffer(previousYear, currentYear);    // Assert   // prettier-ignore   expect(diff).toEqual(     "=== Cars
" +     "+++ Buses
" +     "=== Trains
" +     "+++ Boats
" +     "--- Planes"   ); });