Better attempt at an appengine wrapper.

go/src/infra/gae/libs/wrapper/featurebreaker_test.go

Index: go/src/infra/gae/libs/wrapper/featurebreaker_test.go
diff --git a/go/src/infra/gae/libs/wrapper/featurebreaker_test.go b/go/src/infra/gae/libs/wrapper/featurebreaker_test.go
new file mode 100644
index 0000000000000000000000000000000000000000..3d245084ce8b3f4deddc7114523034b6516eb9bf
--- /dev/null
+++ b/go/src/infra/gae/libs/wrapper/featurebreaker_test.go
@@ -0,0 +1,91 @@
+// Copyright 2015 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 wrapper
+
+import (
+	"fmt"
+	"testing"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+type foo struct {
+	*BrokenFeatures

[M-A Ruel, 2015/05/25 17:14:51]

So this way you could embed the struct, not a pointer.

[iannucci, 2015/05/26 18:25:06]

I won't be able to initialize the map on-demand then, will I?

[M-A Ruel, 2015/05/27 00:27:10]

Yes, since you need to grab the lock in each method anyway.

+}
+
+func (f *foo) Foo() (string, error) {
+	err := f.IsBroken()
+	if err != nil {
+		return "", err
+	}
+	return "foo", nil
+}
+
+func (f *foo) Bar() (string, error) {
+	err := f.IsBroken()
+	if err != nil {
+		return "", err
+	}
+	return "bar", nil
+}
+
+type override struct {
+	*BrokenFeatures
+	totallyRekt bool
+}
+
+func (o *override) IsBroken() error {
+	if o.totallyRekt {
+		return fmt.Errorf("totallyRekt")
+	}
+	return o.BrokenFeatures.IsBroken()
+}
+
+func (o *override) Foo() error {
+	return o.IsBroken()
+}
+
+func TestTestable(t *testing.T) {
+	e := fmt.Errorf("sup")
+	f := foo{NewBrokenFeatures(e)}
+
+	Convey("Testable", t, func() {
+		Convey("can break functions", func() {
+			s, err := f.Foo()
+			So(s, ShouldEqual, "foo")
+			So(err, ShouldBeNil)
+
+			f.SetBrokenFeatures("Foo")
+			_, err = f.Foo()
+			So(err, ShouldEqual, e)
+
+			Convey("and unbreak them", func() {
+				f.UnsetBrokenFeatures("Foo")
+				s, err = f.Foo()
+				So(s, ShouldEqual, "foo")
+				So(err, ShouldBeNil)
+			})
+
+			Convey("and breaking features doesn't break unrelated ones", func() {
+				s, err := f.Bar()
+				So(s, ShouldEqual, "bar")
+				So(err, ShouldBeNil)
+			})
+		})
+
+		Convey("Can override IsBroken too", func() {
+			o := &override{NewBrokenFeatures(e), false}
+			Convey("Can break functions as normal", func() {
+				o.SetBrokenFeatures("Foo")
+				So(o.Foo(), ShouldEqual, e)
+
+				Convey("but can also break them in a user defined way", func() {
+					o.totallyRekt = true
+					So(o.Foo().Error(), ShouldContainSubstring, "totallyRekt")
+				})
+			})
+		})
+	})
+}