cipd: Refactor client to make it more readable.

go/src/infra/tools/cipd/local/testing.go

Index: go/src/infra/tools/cipd/local/testing.go
diff --git a/go/src/infra/tools/cipd/local/testing.go b/go/src/infra/tools/cipd/local/testing.go
new file mode 100644
index 0000000000000000000000000000000000000000..58a53f86a0904c07c298bd0d85299e97006bbf93
--- /dev/null
+++ b/go/src/infra/tools/cipd/local/testing.go
@@ -0,0 +1,58 @@
+// Copyright 2014 The Chromium 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 local
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+)
+
+// NewTestFile returns File implementation (Symlink == false) backed by a fake
+// in-memory data. It is useful in unit tests.
+func NewTestFile(name string, data string, executable bool) File {
+	return &testFile{
+		name:       name,
+		data:       data,
+		executable: executable,
+	}
+}
+
+// NewTestSymlink returns File implementation (Symlink == true) backed by a fake
+// in-memory data. It is useful in unit tests.
+func NewTestSymlink(name string, target string) File {
+	return &testFile{
+		name:          name,
+		symlinkTarget: target,
+	}
+}
+
+type testFile struct {
+	name          string
+	data          string
+	executable    bool
+	symlinkTarget string
+}
+
+func (f *testFile) Name() string     { return f.name }
+func (f *testFile) Size() uint64     { return uint64(len(f.data)) }
+func (f *testFile) Executable() bool { return f.executable }
+func (f *testFile) Symlink() bool    { return f.symlinkTarget != "" }
+
+func (f *testFile) SymlinkTarget() (string, error) {
+	if f.symlinkTarget == "" {
+		return "", fmt.Errorf("Not a symlink: %s", f.Name())
+	}
+	return f.symlinkTarget, nil
+}
+
+func (f *testFile) Open() (io.ReadCloser, error) {
+	if f.Symlink() {
+		return nil, fmt.Errorf("Can't open symlink: %s", f.Name())
+	}
+	r := bytes.NewReader([]byte(f.data))
+	return ioutil.NopCloser(r), nil
+}