strings: additional tests

This CL re-applies the tests added in CL 101330053 and subsequently rolled back in CL 102610043.

The original author of this change was Rui Ueyama <ruiu@google.com>

LGTM=r, ruiu
R=ruiu, r
CC=golang-codereviews
https://golang.org/cl/109170043

diff --git a/src/pkg/strings/replace_test.go b/src/pkg/strings/replace_test.go
index 2cb318b69d7e25884ac41788a48385c0b669c5f3..77e48b988bcefc4638a4828767cd8fd2d623526d 100644 (file)
--- a/src/pkg/strings/replace_test.go
+++ b/src/pkg/strings/replace_test.go
@@ -308,20 +308,21 @@ func TestReplacer(t *testing.T) {
        }
 }
 
+var algorithmTestCases = []struct {
+       r    *Replacer
+       want string
+}{
+       {capitalLetters, "*strings.byteReplacer"},
+       {htmlEscaper, "*strings.byteStringReplacer"},
+       {NewReplacer("12", "123"), "*strings.singleStringReplacer"},
+       {NewReplacer("1", "12"), "*strings.byteStringReplacer"},
+       {NewReplacer("", "X"), "*strings.genericReplacer"},
+       {NewReplacer("a", "1", "b", "12", "cde", "123"), "*strings.genericReplacer"},
+}
+
 // TestPickAlgorithm tests that NewReplacer picks the correct algorithm.
 func TestPickAlgorithm(t *testing.T) {
-       testCases := []struct {
-               r    *Replacer
-               want string
-       }{
-               {capitalLetters, "*strings.byteReplacer"},
-               {htmlEscaper, "*strings.byteStringReplacer"},
-               {NewReplacer("12", "123"), "*strings.singleStringReplacer"},
-               {NewReplacer("1", "12"), "*strings.byteStringReplacer"},
-               {NewReplacer("", "X"), "*strings.genericReplacer"},
-               {NewReplacer("a", "1", "b", "12", "cde", "123"), "*strings.genericReplacer"},
-       }
-       for i, tc := range testCases {
+       for i, tc := range algorithmTestCases {
                got := fmt.Sprintf("%T", tc.r.Replacer())
                if got != tc.want {
                        t.Errorf("%d. algorithm = %s, want %s", i, got, tc.want)
@@ -329,6 +330,23 @@ func TestPickAlgorithm(t *testing.T) {
        }
 }
 
+type errWriter struct{}
+
+func (errWriter) Write(p []byte) (n int, err error) {
+       return 0, fmt.Errorf("unwritable")
+}
+
+// TestWriteStringError tests that WriteString returns an error
+// received from the underlying io.Writer.
+func TestWriteStringError(t *testing.T) {
+       for i, tc := range algorithmTestCases {
+               n, err := tc.r.WriteString(errWriter{}, "abc")
+               if n != 0 || err == nil || err.Error() != "unwritable" {
+                       t.Errorf("%d. WriteStringError = %d, %v, want 0, unwritable", i, n, err)
+               }
+       }
+}
+
 // TestGenericTrieBuilding verifies the structure of the generated trie. There
 // is one node per line, and the key ending with the current line is in the
 // trie if it ends with a "+".