test: add test case for not-equal comparison expr

Author: link-duan

parser_test.go

@@ -7,6 +7,7 @@ func TestParse(t *testing.T) {
 		src      string
 		expected string
 	}{
+		{"=1<>2", "BinaryExpr(Left: LiteralExpr(Value: 1), Operator: <>, Right: LiteralExpr(Value: 2))"},
 		{"=$A:$A", "RangeExpr(CellExpr($A):CellExpr($A))"},
 		{"=$1:1", "RangeExpr(CellExpr($1):CellExpr(1))"},
 		{"=A:B", "RangeExpr(CellExpr(A):CellExpr(B))"},