Write a function which converts the input string to uppercase.

void main() { group("Basic tests", () { test('Testing for "hello"', () => expect(makeUpperCase("hello"), equals("HELLO"))); test('Testing for "hello world"', () => expect(makeUpperCase("hello world"), equals("HELLO WORLD"))); test('Testing for "hello world !"', () => expect(makeUpperCase("hello world !"), equals("HELLO WORLD !"))); test('Testing for "heLlO wORLd !"', () => expect(makeUpperCase("heLlO wORLd !"), equals("HELLO WORLD !"))); test('Testing for "1,2,3 hello world!"', () => expect(makeUpperCase("1,2,3 hello world!"), equals("1,2,3 HELLO WORLD!"))); }); }

내답:

String makeUpperCase(String str) => str.toUpperCase();

String makeUpperCase(String str) => str!= null && str.isNotEmpty ? str.toUpperCase() : '';