Tweak the fakes, add a test of fake.

pkg/kinflate/util/fs/fakefile.go

@@ -17,37 +17,46 @@ limitations under the License.
 package fs
 
 import (
+	"bytes"
 	"os"
-
-	"k8s.io/kubectl/pkg/kinflate/util/fs"
 )
 
-var _ fs.File = &FakeFile{}
+var _ File = &FakeFile{}
 
-// FakeFile implements FileSystem using a fake in-memory filesystem.
+// FakeFile implements File in-memory for tests.
 type FakeFile struct {
 	content []byte
 	open    bool
 }
 
-// Close closes a file.
+// MakeFakeFile makes a fake file.
+func MakeFakeFile() *FakeFile {
+	return &FakeFile{}
+}
+
+// Close marks the fake file closed.
 func (f *FakeFile) Close() error {
 	f.open = false
 	return nil
 }
 
-// Read reads a file's content.
+// Read never fails, and doesn't mutate p.
 func (f *FakeFile) Read(p []byte) (n int, err error) {
 	return len(p), nil
 }
 
-// Write writes bytes to a file
+// Write saves the contents of the argument to memory.
 func (f *FakeFile) Write(p []byte) (n int, err error) {
 	f.content = p
 	return len(p), nil
 }
 
-// Stat returns an interface which has all the information regarding the file.
+// ContentMatches returns true if v matches fake file's content.
+func (f *FakeFile) ContentMatches(v []byte) bool {
+	return bytes.Equal(v, f.content)
+}
+
+// Stat returns nil.
 func (f *FakeFile) Stat() (os.FileInfo, error) {
 	return nil, nil
 }

pkg/kinflate/util/fs/fakefs.go

@@ -17,33 +17,38 @@ limitations under the License.
 package fs
 
 import (
+	"errors"
 	"os"
-
-	"k8s.io/kubectl/pkg/kinflate/util/fs"
 )
 
-var _ fs.FileSystem = &FakeFS{}
+var _ FileSystem = &FakeFS{}
 
 // FakeFS implements FileSystem using a fake in-memory filesystem.
-type FakeFS struct{ m map[string]*FakeFile }
+type FakeFS struct {
+	m map[string]*FakeFile
+}
 
-// Create creates a file given the filename.
-func (fs *FakeFS) Create(name string) (fs.File, error) {
-	if fs.m == nil {
-		fs.m = map[string]*FakeFile{}
-	}
+// MakeFakeFS returns an instance of FakeFS with no files in it.
+func MakeFakeFS() *FakeFS {
+	return &FakeFS{m: map[string]*FakeFile{}}
+}
+
+// Create assures a fake file appears in the in-memory file system.
+func (fs *FakeFS) Create(name string) (File, error) {
 	fs.m[name] = &FakeFile{}
 	return fs.m[name], nil
 }
 
-// Open opens a file given the filename.
-func (fs *FakeFS) Open(name string) (fs.File, error) {
-	if fs.m == nil {
-		fs.m = map[string]*FakeFile{}
-	}
+// Open returns a fake file in the open state.
+func (fs *FakeFS) Open(name string) (File, error) {
 	fs.m[name] = &FakeFile{open: true}
 	return fs.m[name], nil
 }
 
-// Stat return an interface which has all the information regarding the file.
-func (fs *FakeFS) Stat(name string) (os.FileInfo, error) { return os.Stat(name) }
+// Stat always returns nil FileInfo, and returns an error if file does not exist.
+func (fs *FakeFS) Stat(name string) (os.FileInfo, error) {
+	if _, found := fs.m[name]; found {
+		return nil, nil
+	}
+	return nil, errors.New("file does not exist")
+}

pkg/kinflate/util/fs/fakefs_test.go

@@ -0,0 +1,50 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package fs
+
+import (
+	"testing"
+)
+
+func TestStat(t *testing.T) {
+	x := MakeFakeFS()
+	info, err := x.Stat("foo")
+	if info != nil {
+		t.Fatalf("expected nil info")
+	}
+	if err == nil {
+		t.Fatalf("expected error")
+	}
+}
+
+func TestCreate(t *testing.T) {
+	x := MakeFakeFS()
+	f, err := x.Create("foo")
+	if f == nil {
+		t.Fatalf("expected file")
+	}
+	if err != nil {
+		t.Fatalf("unexpected error")
+	}
+	info, err := x.Stat("foo")
+	if info != nil {
+		t.Fatalf("expected nil info")
+	}
+	if err != nil {
+		t.Fatalf("expected no error")
+	}
+}

pkg/kinflate/util/fs/fs.go

@@ -17,19 +17,19 @@ limitations under the License.
 package fs
 
 import (
+	"io"
 	"os"
 )
 
-var _ FileSystem = OSFS{}
+// FileSystem groups basic os filesystem methods.
+type FileSystem interface {
+	Create(name string) (File, error)
+	Open(name string) (File, error)
+	Stat(name string) (os.FileInfo, error)
+}
 
-// OSFS implements FileSystem using the local filesystem.
-type OSFS struct{}
-
-// Create creates a file given the filename.
-func (OSFS) Create(name string) (File, error) { return os.Create(name) }
-
-// Open opens a file given the filename.
-func (OSFS) Open(name string) (File, error) { return os.Open(name) }
-
-// Stat return an interface which has all the information regarding the file.
-func (OSFS) Stat(name string) (os.FileInfo, error) { return os.Stat(name) }
+// File groups the basic os.File methods.
+type File interface {
+	io.ReadWriteCloser
+	Stat() (os.FileInfo, error)
+}

pkg/kinflate/util/fs/realfile.go

@@ -17,22 +17,33 @@ limitations under the License.
 package fs
 
 import (
+	"errors"
 	"os"
 )
 
-var _ File = &OSFile{}
+var _ File = &realFile{}
 
-// OSFile implements File using the local filesystem.
-type OSFile struct{ file *os.File }
+// realFile implements File using the local filesystem.
+type realFile struct {
+	file *os.File
+}
+
+// MakeRealFile makes an instance of realFile.
+func MakeRealFile(f *os.File) (File, error) {
+	if f == nil {
+		return nil, errors.New("file argument may not be nil")
+	}
+	return &realFile{file: f}, nil
+}
 
 // Close closes a file.
-func (f *OSFile) Close() error { return f.file.Close() }
+func (f *realFile) Close() error { return f.file.Close() }
 
 // Read reads a file's content.
-func (f *OSFile) Read(p []byte) (n int, err error) { return f.file.Read(p) }
+func (f *realFile) Read(p []byte) (n int, err error) { return f.file.Read(p) }
 
 // Write writes bytes to a file
-func (f *OSFile) Write(p []byte) (n int, err error) { return f.file.Write(p) }
+func (f *realFile) Write(p []byte) (n int, err error) { return f.file.Write(p) }
 
 // Stat returns an interface which has all the information regarding the file.
-func (f *OSFile) Stat() (os.FileInfo, error) { return f.file.Stat() }
+func (f *realFile) Stat() (os.FileInfo, error) { return f.file.Stat() }

pkg/kinflate/util/fs/realfs.go

@@ -17,19 +17,19 @@ limitations under the License.
 package fs
 
 import (
-	"io"
 	"os"
 )
 
-// FileSystem is the interface that groups the basic filesystem methods.
-type FileSystem interface {
-	Create(name string) (File, error)
-	Open(name string) (File, error)
-	Stat(name string) (os.FileInfo, error)
-}
+var _ FileSystem = RealFS{}
 
-// File is the interface that groups the basic file methods.
-type File interface {
-	io.ReadWriteCloser
-	Stat() (os.FileInfo, error)
-}
+// RealFS implements FileSystem using the local filesystem.
+type RealFS struct{}
+
+// Create delegates to os.Create.
+func (RealFS) Create(name string) (File, error) { return os.Create(name) }
+
+// Open delegates to os.Open.
+func (RealFS) Open(name string) (File, error) { return os.Open(name) }
+
+// Stat delegates to os.Stat.
+func (RealFS) Stat(name string) (os.FileInfo, error) { return os.Stat(name) }