package main import ( "testing" ) // LastIndex returns the index of the last instance of x in list, or // -1 if x is not present. The loop condition has a fault that // causes some tests to fail. Change it to i >= 0 to see them pass. func LastIndex(list []int, x int) int { for i := len(list) - 1; i > 0; i-- { if list[i] == x { return i } } return -1 } func TestLastIndex(t *testing.T) { tests := []struct { list []int x int want int }{ {list: []int{1}, x: 1, want: 0}, {list: []int{1, 1}, x: 1, want: 1}, {list: []int{2, 1}, x: 2, want: 0}, {list: []int{1, 2, 1, 1}, x: 2, want: 1}, {list: []int{1, 1, 1, 2, 2, 1}, x: 3, want: -1}, {list: []int{3, 1, 2, 2, 1, 1}, x: 3, want: 0}, } for _, tt := range tests { if got := LastIndex(tt.list, tt.x); got != tt.want { t.Errorf("LastIndex(%v, %v) = %v, want %v", tt.list, tt.x, got, tt.want) } } }