import capitalizeFirstLetter from './capitalizeFirstLetter' ; interface Test { input : string ; output : string ; } const tests = [ { input : '' , output : '' } , { input : 'this is a sample' , output : 'This is a sample' } , { input : 'this is not going to change' , output : 'This is not going to change' } , { input : 'ALL IN CAPITAL' , output : 'ALL IN CAPITAL' } , { input : 'A Different Case' , output : 'A Different Case' } , { input : '  another case  ' , output : 'Another case' } , ] ; describe ( 'capitalizeFirstLetter' , ( ) => { for ( let i = 0 ; i < tests . length ; i ++ ) { it ( 'returns correct string' , ( ) => { const actual = capitalizeFirstLetter ( tests [ i ] . input ) ; expect ( actual ) . toEqual ( tests [ i ] . output ) ; } ) ; } } ) ;