diff --git a/lexer.go b/lexer.go
index 9b92da5..e7095a4 100644
--- a/lexer.go
+++ b/lexer.go
@@ -27,13 +27,56 @@ const (
 	item_range_close
 )
 
+func (i itemType) String() string {
+	switch i {
+	case item_eof:
+		return "eof"
+
+	case item_error:
+		return "error"
+
+	case item_text:
+		return "text"
+
+	case item_any:
+		return "any"
+
+	case item_single:
+		return "single"
+
+	case item_range_open:
+		return "range_open"
+
+	case item_range_not:
+		return "range_not"
+
+	case item_range_lo:
+		return "range_lo"
+
+	case item_range_minus:
+		return "range_minus"
+
+	case item_range_hi:
+		return "range_hi"
+
+	case item_range_chars:
+		return "range_chars"
+
+	case item_range_close:
+		return "range_close"
+
+	default:
+		return "undef"
+	}
+}
+
 type item struct {
 	t itemType
 	s string
 }
 
 func (i item) String() string {
-	return fmt.Sprintf("%v[%s]", i.t, i.s)
+	return fmt.Sprintf("%v<%s>", i.t, i.s)
 }
 
 type lexer struct {
@@ -193,7 +236,7 @@ func lexInsideRange(l *lexer) stateFn {
 		switch c {
 		case inside_range_not:
 			// only first char makes sense
-			if l.pos == l.start {
+			if l.pos-1 == l.start {
 				l.emit(item_range_not)
 			}
 
@@ -221,6 +264,8 @@ func lexAny(l *lexer) stateFn {
 }
 
 func lexRangeHiLo(l *lexer) stateFn {
+	start := l.start
+
 	for {
 		c := l.read()
 		if c == eof {
@@ -228,22 +273,37 @@ func lexRangeHiLo(l *lexer) stateFn {
 			return nil
 		}
 
-		if l.pos-l.start != 1 {
-			l.errorf("unexpected length of char inside range")
-			return nil
-		}
-
 		switch c {
 		case inside_range_minus:
+			if l.pos-l.start != 1 {
+				l.errorf("unexpected length of range: single character expected before minus")
+				return nil
+			}
+
 			l.emit(item_range_minus)
 
 		case range_close:
 			l.unread()
-			l.flush(item_range_hi)
+
+			if l.pos-l.start != 1 {
+				l.errorf("unexpected length of range: single character expected before close")
+				return nil
+			}
+
+			l.emit(item_range_hi)
 			return lexRangeClose
 
 		default:
-			l.flush(item_range_lo)
+			if start != l.start {
+				continue
+			}
+
+			if l.pos-l.start != 1 {
+				l.errorf("unexpected length of range: single character expected at the begining")
+				return nil
+			}
+
+			l.emit(item_range_lo)
 		}
 	}
 }
diff --git a/lexer_test.go b/lexer_test.go
new file mode 100644
index 0000000..69f3703
--- /dev/null
+++ b/lexer_test.go
@@ -0,0 +1,100 @@
+package glob
+
+import (
+	"testing"
+)
+
+func TestLexGood(t *testing.T) {
+	for _, test := range []struct {
+		pattern string
+		items   []item
+	}{
+		{
+			pattern: "hello",
+			items: []item{
+				item{item_text, "hello"},
+				item{item_eof, ""},
+			},
+		},
+		{
+			pattern: "hello?",
+			items: []item{
+				item{item_text, "hello"},
+				item{item_single, "?"},
+				item{item_eof, ""},
+			},
+		},
+		{
+			pattern: "hello*",
+			items: []item{
+				item{item_text, "hello"},
+				item{item_any, "*"},
+				item{item_eof, ""},
+			},
+		},
+		{
+			pattern: "hello**",
+			items: []item{
+				item{item_text, "hello"},
+				item{item_any, "*"},
+				item{item_any, "*"},
+				item{item_eof, ""},
+			},
+		},
+		{
+			pattern: "[a-b]",
+			items: []item{
+				item{item_range_open, "["},
+				item{item_range_lo, "a"},
+				item{item_range_minus, "-"},
+				item{item_range_hi, "b"},
+				item{item_range_close, "]"},
+				item{item_eof, ""},
+			},
+		},
+		{
+			pattern: "[!a-b]",
+			items: []item{
+				item{item_range_open, "["},
+				item{item_range_not, "!"},
+				item{item_range_lo, "a"},
+				item{item_range_minus, "-"},
+				item{item_range_hi, "b"},
+				item{item_range_close, "]"},
+				item{item_eof, ""},
+			},
+		},
+		{
+			pattern: "[abc]",
+			items: []item{
+				item{item_range_open, "["},
+				item{item_range_chars, "abc"},
+				item{item_range_close, "]"},
+				item{item_eof, ""},
+			},
+		},
+		{
+			pattern: "[!abc]",
+			items: []item{
+				item{item_range_open, "["},
+				item{item_range_not, "!"},
+				item{item_range_chars, "abc"},
+				item{item_range_close, "]"},
+				item{item_eof, ""},
+			},
+		},
+	} {
+		lexer := newLexer(test.pattern)
+		for _, exp := range test.items {
+			act := lexer.nextItem()
+			if act.t != exp.t {
+				t.Errorf("wrong item type: exp: %v; act: %v (%s vs %s)", exp.t, act.t, exp, act)
+				break
+			}
+			if act.s != exp.s {
+				t.Errorf("wrong item contents: exp: %q; act: %q (%s vs %s)", exp.s, act.s, exp, act)
+				break
+			}
+		}
+	}
+}
diff --git a/parser.go b/parser.go
index 761b8b4..d5614f7 100644
--- a/parser.go
+++ b/parser.go
@@ -104,6 +104,10 @@ func parserRange(lexer *lexer, separators string) ([]token, parseFn, error) {
 				return nil, nil, fmt.Errorf("unexpected length of hi character")
 			}
 
+			if hi < lo {
+				return nil, nil, fmt.Errorf("hi character should be greater than lo")
+			}
+
 			hi = r[0]
 
 		case item_range_chars:
@@ -120,6 +124,10 @@ func parserRange(lexer *lexer, separators string) ([]token, parseFn, error) {
 			if isRange {
 				return []token{token{match.Between{lo, hi, not}, ""}}, parserMain, nil
 			} else {
+				if len(chars) == 0 {
+					return nil, nil, fmt.Errorf("chars range should not be empty")
+				}
+
 				return []token{token{match.RangeList{chars, not}, ""}}, parserMain, nil
 			}
 		}
diff --git a/parser_test.go b/parser_test.go
index 31525a6..685d003 100644
--- a/parser_test.go
+++ b/parser_test.go
@@ -1,13 +1,12 @@
 package glob
 
 import (
-	"fmt"
 	"testing"
 )
 
 func TestParseString(t *testing.T) {
-	lexer := newLexer("hello")
-	fmt.Println(lexer.nextItem())
-	fmt.Println(lexer.nextItem())
-	fmt.Println(lexer.nextItem())
+	//	lexer := newLexer("hello")
+	//	fmt.Println(lexer.nextItem())
+	//	fmt.Println(lexer.nextItem())
+	//	fmt.Println(lexer.nextItem())
 }