merge: Add Upper (#862)

String/test/Upper.test.js

@@ -0,0 +1,9 @@
+import { upper } from '../Upper'
+
+describe('Upper', () => {
+  it('return uppercase strings', () => {
+    expect(upper('hello')).toBe('HELLO')
+    expect(upper('WORLD')).toBe('WORLD')
+    expect(upper('hello_WORLD')).toBe('HELLO_WORLD')
+  })
+})