1 files changed, 109 insertions, 0 deletions
diff --git a/src/pkg/utf8/string_test.go b/src/pkg/utf8/string_test.go
new file mode 100644
index 000000000..9dd847247
--- /dev/null
+++ b/src/pkg/utf8/string_test.go
@@ -0,0 +1,109 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package utf8_test
+
+import (
+	"rand"
+	"testing"
+	. "utf8"
+)
+
+func TestScanForwards(t *testing.T) {
+	for _, s := range testStrings {
+		runes := []int(s)
+		str := NewString(s)
+		if str.RuneCount() != len(runes) {
+			t.Errorf("%s: expected %d runes; got %d", s, len(runes), str.RuneCount())
+			break
+		}
+		for i, expect := range runes {
+			got := str.At(i)
+			if got != expect {
+				t.Errorf("%s[%d]: expected %c (%U); got %c (%U)", s, i, expect, expect, got, got)
+			}
+		}
+	}
+}
+
+func TestScanBackwards(t *testing.T) {
+	for _, s := range testStrings {
+		runes := []int(s)
+		str := NewString(s)
+		if str.RuneCount() != len(runes) {
+			t.Errorf("%s: expected %d runes; got %d", s, len(runes), str.RuneCount())
+			break
+		}
+		for i := len(runes) - 1; i >= 0; i-- {
+			expect := runes[i]
+			got := str.At(i)
+			if got != expect {
+				t.Errorf("%s[%d]: expected %c (%U); got %c (%U)", s, i, expect, expect, got, got)
+			}
+		}
+	}
+}
+
+const randCount = 100000
+
+func TestRandomAccess(t *testing.T) {
+	for _, s := range testStrings {
+		if len(s) == 0 {
+			continue
+		}
+		runes := []int(s)
+		str := NewString(s)
+		if str.RuneCount() != len(runes) {
+			t.Errorf("%s: expected %d runes; got %d", s, len(runes), str.RuneCount())
+			break
+		}
+		for j := 0; j < randCount; j++ {
+			i := rand.Intn(len(runes))
+			expect := runes[i]
+			got := str.At(i)
+			if got != expect {
+				t.Errorf("%s[%d]: expected %c (%U); got %c (%U)", s, i, expect, expect, got, got)
+			}
+		}
+	}
+}
+
+func TestRandomSliceAccess(t *testing.T) {
+	for _, s := range testStrings {
+		if len(s) == 0 || s[0] == '\x80' { // the bad-UTF-8 string fools this simple test
+			continue
+		}
+		runes := []int(s)
+		str := NewString(s)
+		if str.RuneCount() != len(runes) {
+			t.Errorf("%s: expected %d runes; got %d", s, len(runes), str.RuneCount())
+			break
+		}
+		for k := 0; k < randCount; k++ {
+			i := rand.Intn(len(runes))
+			j := rand.Intn(len(runes) + 1)
+			if i > j { // include empty strings
+				continue
+			}
+			expect := string(runes[i:j])
+			got := str.Slice(i, j)
+			if got != expect {
+				t.Errorf("%s[%d:%d]: expected %q got %q", s, i, j, expect, got)
+			}
+		}
+	}
+}
+
+func TestLimitSliceAccess(t *testing.T) {
+	for _, s := range testStrings {
+		str := NewString(s)
+		if str.Slice(0, 0) != "" {
+			t.Error("failure with empty slice at beginning")
+		}
+		nr := RuneCountInString(s)
+		if str.Slice(nr, nr) != "" {
+			t.Error("failure with empty slice at end")
+		}
+	}
+}