Update FakeCli to remove duplication in tests.

Use byte buffers by default, since that is what is done most of the time.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

cli/command/checkpoint/create_test.go

@@ -37,7 +37,7 @@ func TestCheckpointCreateErrors(t *testing.T) {
 	}
 
 	for _, tc := range testCases {
-		cli := test.NewFakeCli(&fakeClient{
+		cli := test.NewFakeCliWithOutput(&fakeClient{
 			checkpointCreateFunc: tc.checkpointCreateFunc,
 		}, &bytes.Buffer{})
 		cmd := newCreateCommand(cli)
@@ -51,7 +51,7 @@ func TestCheckpointCreateWithOptions(t *testing.T) {
 	var containerID, checkpointID, checkpointDir string
 	var exit bool
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		checkpointCreateFunc: func(container string, options types.CheckpointCreateOptions) error {
 			containerID = container
 			checkpointID = options.CheckpointID

cli/command/checkpoint/list_test.go

@@ -37,7 +37,7 @@ func TestCheckpointListErrors(t *testing.T) {
 	}
 
 	for _, tc := range testCases {
-		cli := test.NewFakeCli(&fakeClient{
+		cli := test.NewFakeCliWithOutput(&fakeClient{
 			checkpointListFunc: tc.checkpointListFunc,
 		}, &bytes.Buffer{})
 		cmd := newListCommand(cli)
@@ -50,7 +50,7 @@ func TestCheckpointListErrors(t *testing.T) {
 func TestCheckpointListWithOptions(t *testing.T) {
 	var containerID, checkpointDir string
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		checkpointListFunc: func(container string, options types.CheckpointListOptions) ([]types.Checkpoint, error) {
 			containerID = container
 			checkpointDir = options.CheckpointDir

cli/command/checkpoint/remove_test.go

@@ -36,7 +36,7 @@ func TestCheckpointRemoveErrors(t *testing.T) {
 	}
 
 	for _, tc := range testCases {
-		cli := test.NewFakeCli(&fakeClient{
+		cli := test.NewFakeCliWithOutput(&fakeClient{
 			checkpointDeleteFunc: tc.checkpointDeleteFunc,
 		}, &bytes.Buffer{})
 		cmd := newRemoveCommand(cli)
@@ -48,7 +48,7 @@ func TestCheckpointRemoveErrors(t *testing.T) {
 
 func TestCheckpointRemoveWithOptions(t *testing.T) {
 	var containerID, checkpointID, checkpointDir string
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		checkpointDeleteFunc: func(container string, options types.CheckpointDeleteOptions) error {
 			containerID = container
 			checkpointID = options.CheckpointID

cli/command/config/create_test.go

@@ -43,7 +43,7 @@ func TestConfigCreateErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newConfigCreateCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				configCreateFunc: tc.configCreateFunc,
 			}, buf),
 		)
@@ -57,7 +57,7 @@ func TestConfigCreateWithName(t *testing.T) {
 	name := "foo"
 	buf := new(bytes.Buffer)
 	var actual []byte
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		configCreateFunc: func(spec swarm.ConfigSpec) (types.ConfigCreateResponse, error) {
 			if spec.Name != name {
 				return types.ConfigCreateResponse{}, errors.Errorf("expected name %q, got %q", name, spec.Name)
@@ -87,7 +87,7 @@ func TestConfigCreateWithLabels(t *testing.T) {
 	name := "foo"
 
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		configCreateFunc: func(spec swarm.ConfigSpec) (types.ConfigCreateResponse, error) {
 			if spec.Name != name {
 				return types.ConfigCreateResponse{}, errors.Errorf("expected name %q, got %q", name, spec.Name)

cli/command/config/inspect_test.go

@@ -55,7 +55,7 @@ func TestConfigInspectErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newConfigInspectCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				configInspectFunc: tc.configInspectFunc,
 			}, buf),
 		)
@@ -97,7 +97,7 @@ func TestConfigInspectWithoutFormat(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newConfigInspectCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				configInspectFunc: tc.configInspectFunc,
 			}, buf),
 		)
@@ -137,7 +137,7 @@ func TestConfigInspectWithFormat(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newConfigInspectCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				configInspectFunc: tc.configInspectFunc,
 			}, buf),
 		)
@@ -174,7 +174,7 @@ func TestConfigInspectPretty(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newConfigInspectCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				configInspectFunc: tc.configInspectFunc,
 			}, buf))
 		cmd.SetArgs([]string{"configID"})

cli/command/config/ls_test.go

@@ -38,7 +38,7 @@ func TestConfigListErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newConfigListCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				configListFunc: tc.configListFunc,
 			}, buf),
 		)
@@ -50,7 +50,7 @@ func TestConfigListErrors(t *testing.T) {
 
 func TestConfigList(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		configListFunc: func(options types.ConfigListOptions) ([]swarm.Config, error) {
 			return []swarm.Config{
 				*Config(ConfigID("ID-foo"),
@@ -79,7 +79,7 @@ func TestConfigList(t *testing.T) {
 
 func TestConfigListWithQuietOption(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		configListFunc: func(options types.ConfigListOptions) ([]swarm.Config, error) {
 			return []swarm.Config{
 				*Config(ConfigID("ID-foo"), ConfigName("foo")),
@@ -100,7 +100,7 @@ func TestConfigListWithQuietOption(t *testing.T) {
 
 func TestConfigListWithConfigFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		configListFunc: func(options types.ConfigListOptions) ([]swarm.Config, error) {
 			return []swarm.Config{
 				*Config(ConfigID("ID-foo"), ConfigName("foo")),
@@ -122,7 +122,7 @@ func TestConfigListWithConfigFormat(t *testing.T) {
 
 func TestConfigListWithFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		configListFunc: func(options types.ConfigListOptions) ([]swarm.Config, error) {
 			return []swarm.Config{
 				*Config(ConfigID("ID-foo"), ConfigName("foo")),
@@ -142,7 +142,7 @@ func TestConfigListWithFormat(t *testing.T) {
 
 func TestConfigListWithFilter(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		configListFunc: func(options types.ConfigListOptions) ([]swarm.Config, error) {
 			assert.Equal(t, "foo", options.Filters.Get("name")[0])
 			assert.Equal(t, "lbl1=Label-bar", options.Filters.Get("label")[0])

cli/command/config/remove_test.go

@@ -33,7 +33,7 @@ func TestConfigRemoveErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newConfigRemoveCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				configRemoveFunc: tc.configRemoveFunc,
 			}, buf),
 		)
@@ -47,7 +47,7 @@ func TestConfigRemoveWithName(t *testing.T) {
 	names := []string{"foo", "bar"}
 	buf := new(bytes.Buffer)
 	var removedConfigs []string
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		configRemoveFunc: func(name string) error {
 			removedConfigs = append(removedConfigs, name)
 			return nil
@@ -65,7 +65,7 @@ func TestConfigRemoveContinueAfterError(t *testing.T) {
 	buf := new(bytes.Buffer)
 	var removedConfigs []string
 
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		configRemoveFunc: func(name string) error {
 			removedConfigs = append(removedConfigs, name)
 			if name == "foo" {

cli/command/container/attach_test.go

@@ -69,7 +69,7 @@ func TestNewAttachCommandErrors(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cmd := NewAttachCommand(test.NewFakeCli(&fakeClient{containerInspectFunc: tc.containerInspectFunc}, buf))
+		cmd := NewAttachCommand(test.NewFakeCliWithOutput(&fakeClient{containerInspectFunc: tc.containerInspectFunc}, buf))
 		cmd.SetOutput(ioutil.Discard)
 		cmd.SetArgs(tc.args)
 		testutil.ErrorContains(t, cmd.Execute(), tc.expectedError)

cli/command/container/exec_test.go

@@ -140,7 +140,7 @@ func TestNewExecCommandErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		conf := configfile.ConfigFile{}
-		cli := test.NewFakeCli(&fakeClient{containerInspectFunc: tc.containerInspectFunc}, buf)
+		cli := test.NewFakeCliWithOutput(&fakeClient{containerInspectFunc: tc.containerInspectFunc}, buf)
 		cli.SetConfigfile(&conf)
 		cmd := NewExecCommand(cli)
 		cmd.SetOutput(ioutil.Discard)

cli/command/image/build_test.go

@@ -38,7 +38,7 @@ func TestRunBuildDockerfileFromStdinWithCompress(t *testing.T) {
 		return types.ImageBuildResponse{Body: ioutil.NopCloser(body)}, nil
 	}
 
-	cli := test.NewFakeCli(&fakeClient{imageBuildFunc: fakeImageBuild}, ioutil.Discard)
+	cli := test.NewFakeCliWithOutput(&fakeClient{imageBuildFunc: fakeImageBuild}, ioutil.Discard)
 	dockerfile := bytes.NewBufferString(`
 		FROM alpine:3.6
 		COPY foo /

cli/command/image/history_test.go

@@ -39,7 +39,7 @@ func TestNewHistoryCommandErrors(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cmd := NewHistoryCommand(test.NewFakeCli(&fakeClient{imageHistoryFunc: tc.imageHistoryFunc}, buf))
+		cmd := NewHistoryCommand(test.NewFakeCliWithOutput(&fakeClient{imageHistoryFunc: tc.imageHistoryFunc}, buf))
 		cmd.SetOutput(ioutil.Discard)
 		cmd.SetArgs(tc.args)
 		testutil.ErrorContains(t, cmd.Execute(), tc.expectedError)
@@ -91,7 +91,7 @@ func TestNewHistoryCommandSuccess(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cmd := NewHistoryCommand(test.NewFakeCli(&fakeClient{imageHistoryFunc: tc.imageHistoryFunc}, buf))
+		cmd := NewHistoryCommand(test.NewFakeCliWithOutput(&fakeClient{imageHistoryFunc: tc.imageHistoryFunc}, buf))
 		cmd.SetOutput(ioutil.Discard)
 		cmd.SetArgs(tc.args)
 		err := cmd.Execute()

cli/command/image/import_test.go

@@ -37,7 +37,7 @@ func TestNewImportCommandErrors(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cmd := NewImportCommand(test.NewFakeCli(&fakeClient{imageImportFunc: tc.imageImportFunc}, buf))
+		cmd := NewImportCommand(test.NewFakeCliWithOutput(&fakeClient{imageImportFunc: tc.imageImportFunc}, buf))
 		cmd.SetOutput(ioutil.Discard)
 		cmd.SetArgs(tc.args)
 		testutil.ErrorContains(t, cmd.Execute(), tc.expectedError)
@@ -45,7 +45,7 @@ func TestNewImportCommandErrors(t *testing.T) {
 }
 
 func TestNewImportCommandInvalidFile(t *testing.T) {
-	cmd := NewImportCommand(test.NewFakeCli(&fakeClient{}, new(bytes.Buffer)))
+	cmd := NewImportCommand(test.NewFakeCliWithOutput(&fakeClient{}, new(bytes.Buffer)))
 	cmd.SetOutput(ioutil.Discard)
 	cmd.SetArgs([]string{"testdata/import-command-success.unexistent-file"})
 	testutil.ErrorContains(t, cmd.Execute(), "testdata/import-command-success.unexistent-file")
@@ -92,7 +92,7 @@ func TestNewImportCommandSuccess(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cmd := NewImportCommand(test.NewFakeCli(&fakeClient{imageImportFunc: tc.imageImportFunc}, buf))
+		cmd := NewImportCommand(test.NewFakeCliWithOutput(&fakeClient{imageImportFunc: tc.imageImportFunc}, buf))
 		cmd.SetOutput(ioutil.Discard)
 		cmd.SetArgs(tc.args)
 		assert.NoError(t, cmd.Execute())

cli/command/image/inspect_test.go

@@ -27,7 +27,7 @@ func TestNewInspectCommandErrors(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cmd := newInspectCommand(test.NewFakeCli(&fakeClient{}, buf))
+		cmd := newInspectCommand(test.NewFakeCliWithOutput(&fakeClient{}, buf))
 		cmd.SetOutput(ioutil.Discard)
 		cmd.SetArgs(tc.args)
 		testutil.ErrorContains(t, cmd.Execute(), tc.expectedError)
@@ -79,7 +79,7 @@ func TestNewInspectCommandSuccess(t *testing.T) {
 	for _, tc := range testCases {
 		imageInspectInvocationCount = 0
 		buf := new(bytes.Buffer)
-		cmd := newInspectCommand(test.NewFakeCli(&fakeClient{imageInspectFunc: tc.imageInspectFunc}, buf))
+		cmd := newInspectCommand(test.NewFakeCliWithOutput(&fakeClient{imageInspectFunc: tc.imageInspectFunc}, buf))
 		cmd.SetOutput(ioutil.Discard)
 		cmd.SetArgs(tc.args)
 		err := cmd.Execute()

cli/command/image/list_test.go

@@ -36,7 +36,7 @@ func TestNewImagesCommandErrors(t *testing.T) {
 		},
 	}
 	for _, tc := range testCases {
-		cmd := NewImagesCommand(test.NewFakeCli(&fakeClient{imageListFunc: tc.imageListFunc}, new(bytes.Buffer)))
+		cmd := NewImagesCommand(test.NewFakeCliWithOutput(&fakeClient{imageListFunc: tc.imageListFunc}, new(bytes.Buffer)))
 		cmd.SetOutput(ioutil.Discard)
 		cmd.SetArgs(tc.args)
 		testutil.ErrorContains(t, cmd.Execute(), tc.expectedError)
@@ -81,7 +81,7 @@ func TestNewImagesCommandSuccess(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cli := test.NewFakeCli(&fakeClient{imageListFunc: tc.imageListFunc}, buf)
+		cli := test.NewFakeCliWithOutput(&fakeClient{imageListFunc: tc.imageListFunc}, buf)
 		cli.SetConfigfile(&configfile.ConfigFile{ImagesFormat: tc.imageFormat})
 		cmd := NewImagesCommand(cli)
 		cmd.SetOutput(ioutil.Discard)
@@ -95,7 +95,7 @@ func TestNewImagesCommandSuccess(t *testing.T) {
 }
 
 func TestNewListCommandAlias(t *testing.T) {
-	cmd := newListCommand(test.NewFakeCli(&fakeClient{}, new(bytes.Buffer)))
+	cmd := newListCommand(test.NewFakeCliWithOutput(&fakeClient{}, new(bytes.Buffer)))
 	assert.True(t, cmd.HasAlias("images"))
 	assert.True(t, cmd.HasAlias("list"))
 	assert.False(t, cmd.HasAlias("other"))

cli/command/image/load_test.go

@@ -43,7 +43,7 @@ func TestNewLoadCommandErrors(t *testing.T) {
 		},
 	}
 	for _, tc := range testCases {
-		cli := test.NewFakeCli(&fakeClient{imageLoadFunc: tc.imageLoadFunc}, new(bytes.Buffer))
+		cli := test.NewFakeCliWithOutput(&fakeClient{imageLoadFunc: tc.imageLoadFunc}, new(bytes.Buffer))
 		cli.In().SetIsTerminal(tc.isTerminalIn)
 		cmd := NewLoadCommand(cli)
 		cmd.SetOutput(ioutil.Discard)
@@ -54,7 +54,7 @@ func TestNewLoadCommandErrors(t *testing.T) {
 
 func TestNewLoadCommandInvalidInput(t *testing.T) {
 	expectedError := "open *"
-	cmd := NewLoadCommand(test.NewFakeCli(&fakeClient{}, new(bytes.Buffer)))
+	cmd := NewLoadCommand(test.NewFakeCliWithOutput(&fakeClient{}, new(bytes.Buffer)))
 	cmd.SetOutput(ioutil.Discard)
 	cmd.SetArgs([]string{"--input", "*"})
 	err := cmd.Execute()
@@ -93,7 +93,7 @@ func TestNewLoadCommandSuccess(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cmd := NewLoadCommand(test.NewFakeCli(&fakeClient{imageLoadFunc: tc.imageLoadFunc}, buf))
+		cmd := NewLoadCommand(test.NewFakeCliWithOutput(&fakeClient{imageLoadFunc: tc.imageLoadFunc}, buf))
 		cmd.SetOutput(ioutil.Discard)
 		cmd.SetArgs(tc.args)
 		err := cmd.Execute()

cli/command/image/prune_test.go

@@ -38,7 +38,7 @@ func TestNewPruneCommandErrors(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cmd := NewPruneCommand(test.NewFakeCli(&fakeClient{
+		cmd := NewPruneCommand(test.NewFakeCliWithOutput(&fakeClient{
 			imagesPruneFunc: tc.imagesPruneFunc,
 		}, buf))
 		cmd.SetOutput(ioutil.Discard)
@@ -86,7 +86,7 @@ func TestNewPruneCommandSuccess(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cmd := NewPruneCommand(test.NewFakeCli(&fakeClient{
+		cmd := NewPruneCommand(test.NewFakeCliWithOutput(&fakeClient{
 			imagesPruneFunc: tc.imagesPruneFunc,
 		}, buf))
 		cmd.SetOutput(ioutil.Discard)

cli/command/image/pull_test.go

@@ -42,7 +42,7 @@ func TestNewPullCommandErrors(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cli := test.NewFakeCli(&fakeClient{}, buf)
+		cli := test.NewFakeCliWithOutput(&fakeClient{}, buf)
 		cli.SetConfigfile(configfile.New("filename"))
 		cmd := NewPullCommand(cli)
 		cmd.SetOutput(ioutil.Discard)
@@ -67,7 +67,7 @@ func TestNewPullCommandSuccess(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cli := test.NewFakeCli(&fakeClient{}, buf)
+		cli := test.NewFakeCliWithOutput(&fakeClient{}, buf)
 		cli.SetConfigfile(configfile.New("filename"))
 		cmd := NewPullCommand(cli)
 		cmd.SetOutput(ioutil.Discard)

cli/command/image/push_test.go

@@ -48,7 +48,7 @@ func TestNewPushCommandErrors(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cli := test.NewFakeCli(&fakeClient{imagePushFunc: tc.imagePushFunc}, buf)
+		cli := test.NewFakeCliWithOutput(&fakeClient{imagePushFunc: tc.imagePushFunc}, buf)
 		cli.SetConfigfile(configfile.New("filename"))
 		cmd := NewPushCommand(cli)
 		cmd.SetOutput(ioutil.Discard)
@@ -69,7 +69,7 @@ func TestNewPushCommandSuccess(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cli := test.NewFakeCli(&fakeClient{
+		cli := test.NewFakeCliWithOutput(&fakeClient{
 			imagePushFunc: func(ref string, options types.ImagePushOptions) (io.ReadCloser, error) {
 				return ioutil.NopCloser(strings.NewReader("")), nil
 			},

cli/command/image/remove_test.go

@@ -15,7 +15,7 @@ import (
 )
 
 func TestNewRemoveCommandAlias(t *testing.T) {
-	cmd := newRemoveCommand(test.NewFakeCli(&fakeClient{}, new(bytes.Buffer)))
+	cmd := newRemoveCommand(test.NewFakeCliWithOutput(&fakeClient{}, new(bytes.Buffer)))
 	assert.True(t, cmd.HasAlias("rmi"))
 	assert.True(t, cmd.HasAlias("remove"))
 	assert.False(t, cmd.HasAlias("other"))
@@ -44,7 +44,7 @@ func TestNewRemoveCommandErrors(t *testing.T) {
 		},
 	}
 	for _, tc := range testCases {
-		cmd := NewRemoveCommand(test.NewFakeCli(&fakeClient{
+		cmd := NewRemoveCommand(test.NewFakeCliWithOutput(&fakeClient{
 			imageRemoveFunc: tc.imageRemoveFunc,
 		}, new(bytes.Buffer)))
 		cmd.SetOutput(ioutil.Discard)
@@ -99,7 +99,7 @@ func TestNewRemoveCommandSuccess(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		errBuf := new(bytes.Buffer)
-		fakeCli := test.NewFakeCli(&fakeClient{imageRemoveFunc: tc.imageRemoveFunc}, buf)
+		fakeCli := test.NewFakeCliWithOutput(&fakeClient{imageRemoveFunc: tc.imageRemoveFunc}, buf)
 		fakeCli.SetErr(errBuf)
 		cmd := NewRemoveCommand(fakeCli)
 		cmd.SetOutput(ioutil.Discard)

cli/command/image/save_test.go

@@ -45,7 +45,7 @@ func TestNewSaveCommandErrors(t *testing.T) {
 		},
 	}
 	for _, tc := range testCases {
-		cli := test.NewFakeCli(&fakeClient{imageSaveFunc: tc.imageSaveFunc}, new(bytes.Buffer))
+		cli := test.NewFakeCliWithOutput(&fakeClient{imageSaveFunc: tc.imageSaveFunc}, new(bytes.Buffer))
 		cli.Out().SetIsTerminal(tc.isTerminal)
 		cmd := NewSaveCommand(cli)
 		cmd.SetOutput(ioutil.Discard)
@@ -85,7 +85,7 @@ func TestNewSaveCommandSuccess(t *testing.T) {
 		},
 	}
 	for _, tc := range testCases {
-		cmd := NewSaveCommand(test.NewFakeCli(&fakeClient{
+		cmd := NewSaveCommand(test.NewFakeCliWithOutput(&fakeClient{
 			imageSaveFunc: func(images []string) (io.ReadCloser, error) {
 				return ioutil.NopCloser(strings.NewReader("")), nil
 			},

cli/command/image/tag_test.go

@@ -19,7 +19,7 @@ func TestCliNewTagCommandErrors(t *testing.T) {
 	expectedError := "\"tag\" requires exactly 2 argument(s)."
 	buf := new(bytes.Buffer)
 	for _, args := range testCases {
-		cmd := NewTagCommand(test.NewFakeCli(&fakeClient{}, buf))
+		cmd := NewTagCommand(test.NewFakeCliWithOutput(&fakeClient{}, buf))
 		cmd.SetArgs(args)
 		cmd.SetOutput(ioutil.Discard)
 		testutil.ErrorContains(t, cmd.Execute(), expectedError)
@@ -29,7 +29,7 @@ func TestCliNewTagCommandErrors(t *testing.T) {
 func TestCliNewTagCommand(t *testing.T) {
 	buf := new(bytes.Buffer)
 	cmd := NewTagCommand(
-		test.NewFakeCli(&fakeClient{
+		test.NewFakeCliWithOutput(&fakeClient{
 			imageTagFunc: func(image string, ref string) error {
 				assert.Equal(t, "image1", image)
 				assert.Equal(t, "image2", ref)

cli/command/node/demote_test.go

@@ -42,7 +42,7 @@ func TestNodeDemoteErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newDemoteCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				nodeInspectFunc: tc.nodeInspectFunc,
 				nodeUpdateFunc:  tc.nodeUpdateFunc,
 			}, buf))
@@ -55,7 +55,7 @@ func TestNodeDemoteErrors(t *testing.T) {
 func TestNodeDemoteNoChange(t *testing.T) {
 	buf := new(bytes.Buffer)
 	cmd := newDemoteCommand(
-		test.NewFakeCli(&fakeClient{
+		test.NewFakeCliWithOutput(&fakeClient{
 			nodeInspectFunc: func() (swarm.Node, []byte, error) {
 				return *Node(), []byte{}, nil
 			},
@@ -73,7 +73,7 @@ func TestNodeDemoteNoChange(t *testing.T) {
 func TestNodeDemoteMultipleNode(t *testing.T) {
 	buf := new(bytes.Buffer)
 	cmd := newDemoteCommand(
-		test.NewFakeCli(&fakeClient{
+		test.NewFakeCliWithOutput(&fakeClient{
 			nodeInspectFunc: func() (swarm.Node, []byte, error) {
 				return *Node(Manager()), []byte{}, nil
 			},

cli/command/node/inspect_test.go

@@ -69,7 +69,7 @@ func TestNodeInspectErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newInspectCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				nodeInspectFunc: tc.nodeInspectFunc,
 				infoFunc:        tc.infoFunc,
 			}, buf))
@@ -111,7 +111,7 @@ func TestNodeInspectPretty(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newInspectCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				nodeInspectFunc: tc.nodeInspectFunc,
 			}, buf))
 		cmd.SetArgs([]string{"nodeID"})

cli/command/node/list_test.go

@@ -43,7 +43,7 @@ func TestNodeListErrorOnAPIFailure(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cli := test.NewFakeCli(&fakeClient{
+		cli := test.NewFakeCliWithOutput(&fakeClient{
 			nodeListFunc: tc.nodeListFunc,
 			infoFunc:     tc.infoFunc,
 		}, buf)
@@ -56,7 +56,7 @@ func TestNodeListErrorOnAPIFailure(t *testing.T) {
 
 func TestNodeList(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		nodeListFunc: func() ([]swarm.Node, error) {
 			return []swarm.Node{
 				*Node(NodeID("nodeID1"), Hostname("nodeHostname1"), Manager(Leader())),
@@ -82,7 +82,7 @@ func TestNodeList(t *testing.T) {
 
 func TestNodeListQuietShouldOnlyPrintIDs(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		nodeListFunc: func() ([]swarm.Node, error) {
 			return []swarm.Node{
 				*Node(),
@@ -99,7 +99,7 @@ func TestNodeListQuietShouldOnlyPrintIDs(t *testing.T) {
 // Test case for #24090
 func TestNodeListContainsHostname(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{}, buf)
+	cli := test.NewFakeCliWithOutput(&fakeClient{}, buf)
 	cli.SetConfigfile(&configfile.ConfigFile{})
 	cmd := newListCommand(cli)
 	assert.NoError(t, cmd.Execute())
@@ -108,7 +108,7 @@ func TestNodeListContainsHostname(t *testing.T) {
 
 func TestNodeListDefaultFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		nodeListFunc: func() ([]swarm.Node, error) {
 			return []swarm.Node{
 				*Node(NodeID("nodeID1"), Hostname("nodeHostname1"), Manager(Leader())),
@@ -136,7 +136,7 @@ func TestNodeListDefaultFormat(t *testing.T) {
 
 func TestNodeListFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		nodeListFunc: func() ([]swarm.Node, error) {
 			return []swarm.Node{
 				*Node(NodeID("nodeID1"), Hostname("nodeHostname1"), Manager(Leader())),

cli/command/node/promote_test.go

@@ -42,7 +42,7 @@ func TestNodePromoteErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newPromoteCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				nodeInspectFunc: tc.nodeInspectFunc,
 				nodeUpdateFunc:  tc.nodeUpdateFunc,
 			}, buf))
@@ -55,7 +55,7 @@ func TestNodePromoteErrors(t *testing.T) {
 func TestNodePromoteNoChange(t *testing.T) {
 	buf := new(bytes.Buffer)
 	cmd := newPromoteCommand(
-		test.NewFakeCli(&fakeClient{
+		test.NewFakeCliWithOutput(&fakeClient{
 			nodeInspectFunc: func() (swarm.Node, []byte, error) {
 				return *Node(Manager()), []byte{}, nil
 			},
@@ -73,7 +73,7 @@ func TestNodePromoteNoChange(t *testing.T) {
 func TestNodePromoteMultipleNode(t *testing.T) {
 	buf := new(bytes.Buffer)
 	cmd := newPromoteCommand(
-		test.NewFakeCli(&fakeClient{
+		test.NewFakeCliWithOutput(&fakeClient{
 			nodeInspectFunc: func() (swarm.Node, []byte, error) {
 				return *Node(), []byte{}, nil
 			},

cli/command/node/ps_test.go

@@ -52,7 +52,7 @@ func TestNodePsErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newPsCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				infoFunc:        tc.infoFunc,
 				nodeInspectFunc: tc.nodeInspectFunc,
 				taskInspectFunc: tc.taskInspectFunc,
@@ -116,7 +116,7 @@ func TestNodePs(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newPsCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				infoFunc:        tc.infoFunc,
 				nodeInspectFunc: tc.nodeInspectFunc,
 				taskInspectFunc: tc.taskInspectFunc,

cli/command/node/remove_test.go

@@ -31,7 +31,7 @@ func TestNodeRemoveErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newRemoveCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				nodeRemoveFunc: tc.nodeRemoveFunc,
 			}, buf))
 		cmd.SetArgs(tc.args)
@@ -42,7 +42,7 @@ func TestNodeRemoveErrors(t *testing.T) {
 
 func TestNodeRemoveMultiple(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cmd := newRemoveCommand(test.NewFakeCli(&fakeClient{}, buf))
+	cmd := newRemoveCommand(test.NewFakeCliWithOutput(&fakeClient{}, buf))
 	cmd.SetArgs([]string{"nodeID1", "nodeID2"})
 	assert.NoError(t, cmd.Execute())
 }

cli/command/node/update_test.go

@@ -59,7 +59,7 @@ func TestNodeUpdateErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newUpdateCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				nodeInspectFunc: tc.nodeInspectFunc,
 				nodeUpdateFunc:  tc.nodeUpdateFunc,
 			}, buf))
@@ -160,7 +160,7 @@ func TestNodeUpdate(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newUpdateCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				nodeInspectFunc: tc.nodeInspectFunc,
 				nodeUpdateFunc:  tc.nodeUpdateFunc,
 			}, buf))

cli/command/registry_test.go

@@ -64,7 +64,7 @@ func TestElectAuthServer(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
-		cli := test.NewFakeCli(&fakeClient{infoFunc: tc.infoFunc}, buf)
+		cli := test.NewFakeCliWithOutput(&fakeClient{infoFunc: tc.infoFunc}, buf)
 		errBuf := new(bytes.Buffer)
 		cli.SetErr(errBuf)
 		server := ElectAuthServer(context.Background(), cli)

cli/command/secret/create_test.go

@@ -43,7 +43,7 @@ func TestSecretCreateErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newSecretCreateCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				secretCreateFunc: tc.secretCreateFunc,
 			}, buf),
 		)
@@ -57,7 +57,7 @@ func TestSecretCreateWithName(t *testing.T) {
 	name := "foo"
 	buf := new(bytes.Buffer)
 	var actual []byte
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		secretCreateFunc: func(spec swarm.SecretSpec) (types.SecretCreateResponse, error) {
 			if spec.Name != name {
 				return types.SecretCreateResponse{}, errors.Errorf("expected name %q, got %q", name, spec.Name)
@@ -87,7 +87,7 @@ func TestSecretCreateWithLabels(t *testing.T) {
 	name := "foo"
 
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		secretCreateFunc: func(spec swarm.SecretSpec) (types.SecretCreateResponse, error) {
 			if spec.Name != name {
 				return types.SecretCreateResponse{}, errors.Errorf("expected name %q, got %q", name, spec.Name)

cli/command/secret/inspect_test.go

@@ -55,7 +55,7 @@ func TestSecretInspectErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newSecretInspectCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				secretInspectFunc: tc.secretInspectFunc,
 			}, buf),
 		)
@@ -97,7 +97,7 @@ func TestSecretInspectWithoutFormat(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newSecretInspectCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				secretInspectFunc: tc.secretInspectFunc,
 			}, buf),
 		)
@@ -137,7 +137,7 @@ func TestSecretInspectWithFormat(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newSecretInspectCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				secretInspectFunc: tc.secretInspectFunc,
 			}, buf),
 		)
@@ -173,7 +173,7 @@ func TestSecretInspectPretty(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newSecretInspectCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				secretInspectFunc: tc.secretInspectFunc,
 			}, buf))
 		cmd.SetArgs([]string{"secretID"})

cli/command/secret/ls_test.go

@@ -38,7 +38,7 @@ func TestSecretListErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newSecretListCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				secretListFunc: tc.secretListFunc,
 			}, buf),
 		)
@@ -50,7 +50,7 @@ func TestSecretListErrors(t *testing.T) {
 
 func TestSecretList(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		secretListFunc: func(options types.SecretListOptions) ([]swarm.Secret, error) {
 			return []swarm.Secret{
 				*Secret(SecretID("ID-foo"),
@@ -79,7 +79,7 @@ func TestSecretList(t *testing.T) {
 
 func TestSecretListWithQuietOption(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		secretListFunc: func(options types.SecretListOptions) ([]swarm.Secret, error) {
 			return []swarm.Secret{
 				*Secret(SecretID("ID-foo"), SecretName("foo")),
@@ -100,7 +100,7 @@ func TestSecretListWithQuietOption(t *testing.T) {
 
 func TestSecretListWithConfigFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		secretListFunc: func(options types.SecretListOptions) ([]swarm.Secret, error) {
 			return []swarm.Secret{
 				*Secret(SecretID("ID-foo"), SecretName("foo")),
@@ -122,7 +122,7 @@ func TestSecretListWithConfigFormat(t *testing.T) {
 
 func TestSecretListWithFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		secretListFunc: func(options types.SecretListOptions) ([]swarm.Secret, error) {
 			return []swarm.Secret{
 				*Secret(SecretID("ID-foo"), SecretName("foo")),
@@ -142,7 +142,7 @@ func TestSecretListWithFormat(t *testing.T) {
 
 func TestSecretListWithFilter(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		secretListFunc: func(options types.SecretListOptions) ([]swarm.Secret, error) {
 			assert.Equal(t, "foo", options.Filters.Get("name")[0], "foo")
 			assert.Equal(t, "lbl1=Label-bar", options.Filters.Get("label")[0])

cli/command/secret/remove_test.go

@@ -33,7 +33,7 @@ func TestSecretRemoveErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newSecretRemoveCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				secretRemoveFunc: tc.secretRemoveFunc,
 			}, buf),
 		)
@@ -47,7 +47,7 @@ func TestSecretRemoveWithName(t *testing.T) {
 	names := []string{"foo", "bar"}
 	buf := new(bytes.Buffer)
 	var removedSecrets []string
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		secretRemoveFunc: func(name string) error {
 			removedSecrets = append(removedSecrets, name)
 			return nil
@@ -65,7 +65,7 @@ func TestSecretRemoveContinueAfterError(t *testing.T) {
 	buf := new(bytes.Buffer)
 	var removedSecrets []string
 
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		secretRemoveFunc: func(name string) error {
 			removedSecrets = append(removedSecrets, name)
 			if name == "foo" {

cli/command/service/ps_test.go

@@ -107,7 +107,7 @@ func TestRunPSWarnsOnNotFound(t *testing.T) {
 	}
 
 	out := new(bytes.Buffer)
-	cli := test.NewFakeCli(client, out)
+	cli := test.NewFakeCliWithOutput(client, out)
 	options := psOptions{
 		services: []string{"foo", "bar"},
 		filter:   opts.NewFilterOpt(),

cli/command/stack/deploy_test.go

@@ -18,7 +18,7 @@ func TestPruneServices(t *testing.T) {
 		"keep": {},
 	}
 	client := &fakeClient{services: []string{objectName("foo", "keep"), objectName("foo", "remove")}}
-	dockerCli := test.NewFakeCli(client, &bytes.Buffer{})
+	dockerCli := test.NewFakeCliWithOutput(client, &bytes.Buffer{})
 	dockerCli.SetErr(&bytes.Buffer{})
 
 	pruneServices(ctx, dockerCli, namespace, services)

cli/command/stack/list_test.go

@@ -48,7 +48,7 @@ func TestListErrors(t *testing.T) {
 	}
 
 	for _, tc := range testCases {
-		cmd := newListCommand(test.NewFakeCli(&fakeClient{
+		cmd := newListCommand(test.NewFakeCliWithOutput(&fakeClient{
 			serviceListFunc: tc.serviceListFunc,
 		}, &bytes.Buffer{}))
 		cmd.SetArgs(tc.args)
@@ -62,7 +62,7 @@ func TestListErrors(t *testing.T) {
 
 func TestListWithFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cmd := newListCommand(test.NewFakeCli(&fakeClient{
+	cmd := newListCommand(test.NewFakeCliWithOutput(&fakeClient{
 		serviceListFunc: func(options types.ServiceListOptions) ([]swarm.Service, error) {
 			return []swarm.Service{
 				*Service(
@@ -81,7 +81,7 @@ func TestListWithFormat(t *testing.T) {
 
 func TestListWithoutFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cmd := newListCommand(test.NewFakeCli(&fakeClient{
+	cmd := newListCommand(test.NewFakeCliWithOutput(&fakeClient{
 		serviceListFunc: func(options types.ServiceListOptions) ([]swarm.Service, error) {
 			return []swarm.Service{
 				*Service(
@@ -99,7 +99,7 @@ func TestListWithoutFormat(t *testing.T) {
 
 func TestListOrder(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cmd := newListCommand(test.NewFakeCli(&fakeClient{
+	cmd := newListCommand(test.NewFakeCliWithOutput(&fakeClient{
 		serviceListFunc: func(options types.ServiceListOptions) ([]swarm.Service, error) {
 			return []swarm.Service{
 				*Service(

cli/command/stack/ps_test.go

@@ -43,7 +43,7 @@ func TestStackPsErrors(t *testing.T) {
 	}
 
 	for _, tc := range testCases {
-		cmd := newPsCommand(test.NewFakeCli(&fakeClient{
+		cmd := newPsCommand(test.NewFakeCliWithOutput(&fakeClient{
 			taskListFunc: tc.taskListFunc,
 		}, &bytes.Buffer{}))
 		cmd.SetArgs(tc.args)
@@ -53,25 +53,22 @@ func TestStackPsErrors(t *testing.T) {
 }
 
 func TestStackPsEmptyStack(t *testing.T) {
-	out := new(bytes.Buffer)
-	stderr := new(bytes.Buffer)
 	fakeCli := test.NewFakeCli(&fakeClient{
 		taskListFunc: func(options types.TaskListOptions) ([]swarm.Task, error) {
 			return []swarm.Task{}, nil
 		},
-	}, out)
+	})
-	fakeCli.SetErr(stderr)
 	cmd := newPsCommand(fakeCli)
 	cmd.SetArgs([]string{"foo"})
 
 	assert.NoError(t, cmd.Execute())
-	assert.Equal(t, "", out.String())
+	assert.Equal(t, "", fakeCli.OutBuffer().String())
-	assert.Equal(t, "Nothing found in stack: foo\n", stderr.String())
+	assert.Equal(t, "Nothing found in stack: foo\n", fakeCli.ErrBuffer().String())
 }
 
 func TestStackPsWithQuietOption(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		taskListFunc: func(options types.TaskListOptions) ([]swarm.Task, error) {
 			return []swarm.Task{*Task(TaskID("id-foo"))}, nil
 		},
@@ -89,7 +86,7 @@ func TestStackPsWithQuietOption(t *testing.T) {
 
 func TestStackPsWithNoTruncOption(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		taskListFunc: func(options types.TaskListOptions) ([]swarm.Task, error) {
 			return []swarm.Task{*Task(TaskID("xn4cypcov06f2w8gsbaf2lst3"))}, nil
 		},
@@ -107,7 +104,7 @@ func TestStackPsWithNoTruncOption(t *testing.T) {
 
 func TestStackPsWithNoResolveOption(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		taskListFunc: func(options types.TaskListOptions) ([]swarm.Task, error) {
 			return []swarm.Task{*Task(
 				TaskNodeID("id-node-foo"),
@@ -130,7 +127,7 @@ func TestStackPsWithNoResolveOption(t *testing.T) {
 
 func TestStackPsWithFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		taskListFunc: func(options types.TaskListOptions) ([]swarm.Task, error) {
 			return []swarm.Task{*Task(TaskServiceID("service-id-foo"))}, nil
 		},
@@ -147,7 +144,7 @@ func TestStackPsWithFormat(t *testing.T) {
 
 func TestStackPsWithConfigFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		taskListFunc: func(options types.TaskListOptions) ([]swarm.Task, error) {
 			return []swarm.Task{*Task(TaskServiceID("service-id-foo"))}, nil
 		},
@@ -165,7 +162,7 @@ func TestStackPsWithConfigFormat(t *testing.T) {
 
 func TestStackPsWithoutFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		taskListFunc: func(options types.TaskListOptions) ([]swarm.Task, error) {
 			return []swarm.Task{*Task(
 				TaskID("id-foo"),

cli/command/stack/remove_test.go

@@ -46,7 +46,7 @@ func TestRemoveStack(t *testing.T) {
 		secrets:  allSecrets,
 		configs:  allConfigs,
 	}
-	cmd := newRemoveCommand(test.NewFakeCli(cli, &bytes.Buffer{}))
+	cmd := newRemoveCommand(test.NewFakeCliWithOutput(cli, &bytes.Buffer{}))
 	cmd.SetArgs([]string{"foo", "bar"})
 
 	assert.NoError(t, cmd.Execute())
@@ -57,8 +57,6 @@ func TestRemoveStack(t *testing.T) {
 }
 
 func TestRemoveStackSkipEmpty(t *testing.T) {
-	out := new(bytes.Buffer)
-	stderr := new(bytes.Buffer)
 	allServices := []string{objectName("bar", "service1"), objectName("bar", "service2")}
 	allServiceIDs := buildObjectIDs(allServices)
 
@@ -77,14 +75,13 @@ func TestRemoveStackSkipEmpty(t *testing.T) {
 		secrets:  allSecrets,
 		configs:  allConfigs,
 	}
-	fakeCli := test.NewFakeCli(fakeClient, out)
+	fakeCli := test.NewFakeCli(fakeClient)
-	fakeCli.SetErr(stderr)
 	cmd := newRemoveCommand(fakeCli)
 	cmd.SetArgs([]string{"foo", "bar"})
 
 	assert.NoError(t, cmd.Execute())
-	assert.Equal(t, "", out.String())
+	assert.Equal(t, "", fakeCli.OutBuffer().String())
-	assert.Contains(t, stderr.String(), "Nothing found in stack: foo\n")
+	assert.Contains(t, fakeCli.ErrBuffer().String(), "Nothing found in stack: foo\n")
 	assert.Equal(t, allServiceIDs, fakeClient.removedServices)
 	assert.Equal(t, allNetworkIDs, fakeClient.removedNetworks)
 	assert.Equal(t, allSecretIDs, fakeClient.removedSecrets)
@@ -120,7 +117,7 @@ func TestRemoveContinueAfterError(t *testing.T) {
 			return nil
 		},
 	}
-	cmd := newRemoveCommand(test.NewFakeCli(cli, &bytes.Buffer{}))
+	cmd := newRemoveCommand(test.NewFakeCliWithOutput(cli, &bytes.Buffer{}))
 	cmd.SetOutput(ioutil.Discard)
 	cmd.SetArgs([]string{"foo", "bar"})
 

cli/command/stack/services_test.go

@@ -66,7 +66,7 @@ func TestStackServicesErrors(t *testing.T) {
 	}
 
 	for _, tc := range testCases {
-		cli := test.NewFakeCli(&fakeClient{
+		cli := test.NewFakeCliWithOutput(&fakeClient{
 			serviceListFunc: tc.serviceListFunc,
 			nodeListFunc:    tc.nodeListFunc,
 			taskListFunc:    tc.taskListFunc,
@@ -83,24 +83,21 @@ func TestStackServicesErrors(t *testing.T) {
 }
 
 func TestStackServicesEmptyServiceList(t *testing.T) {
-	out := new(bytes.Buffer)
-	stderr := new(bytes.Buffer)
 	fakeCli := test.NewFakeCli(&fakeClient{
 		serviceListFunc: func(options types.ServiceListOptions) ([]swarm.Service, error) {
 			return []swarm.Service{}, nil
 		},
-	}, out)
+	})
-	fakeCli.SetErr(stderr)
 	cmd := newServicesCommand(fakeCli)
 	cmd.SetArgs([]string{"foo"})
 	assert.NoError(t, cmd.Execute())
-	assert.Equal(t, "", out.String())
+	assert.Equal(t, "", fakeCli.OutBuffer().String())
-	assert.Equal(t, "Nothing found in stack: foo\n", stderr.String())
+	assert.Equal(t, "Nothing found in stack: foo\n", fakeCli.ErrBuffer().String())
 }
 
 func TestStackServicesWithQuietOption(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		serviceListFunc: func(options types.ServiceListOptions) ([]swarm.Service, error) {
 			return []swarm.Service{*Service(ServiceID("id-foo"))}, nil
 		},
@@ -117,7 +114,7 @@ func TestStackServicesWithQuietOption(t *testing.T) {
 
 func TestStackServicesWithFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		serviceListFunc: func(options types.ServiceListOptions) ([]swarm.Service, error) {
 			return []swarm.Service{
 				*Service(ServiceName("service-name-foo")),
@@ -136,7 +133,7 @@ func TestStackServicesWithFormat(t *testing.T) {
 
 func TestStackServicesWithConfigFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		serviceListFunc: func(options types.ServiceListOptions) ([]swarm.Service, error) {
 			return []swarm.Service{
 				*Service(ServiceName("service-name-foo")),
@@ -156,7 +153,7 @@ func TestStackServicesWithConfigFormat(t *testing.T) {
 
 func TestStackServicesWithoutFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		serviceListFunc: func(options types.ServiceListOptions) ([]swarm.Service, error) {
 			return []swarm.Service{*Service(
 				ServiceName("name-foo"),

cli/command/swarm/init_test.go

@@ -67,7 +67,7 @@ func TestSwarmInitErrorOnAPIFailure(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newInitCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				swarmInitFunc:         tc.swarmInitFunc,
 				swarmInspectFunc:      tc.swarmInspectFunc,
 				swarmGetUnlockKeyFunc: tc.swarmGetUnlockKeyFunc,
@@ -114,7 +114,7 @@ func TestSwarmInit(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newInitCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				swarmInitFunc:         tc.swarmInitFunc,
 				swarmInspectFunc:      tc.swarmInspectFunc,
 				swarmGetUnlockKeyFunc: tc.swarmGetUnlockKeyFunc,

cli/command/swarm/join_test.go

@@ -51,7 +51,7 @@ func TestSwarmJoinErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newJoinCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				swarmJoinFunc: tc.swarmJoinFunc,
 				infoFunc:      tc.infoFunc,
 			}, buf))
@@ -93,7 +93,7 @@ func TestSwarmJoin(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newJoinCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				infoFunc: tc.infoFunc,
 			}, buf))
 		cmd.SetArgs([]string{"remote"})

cli/command/swarm/join_token_test.go

@@ -92,7 +92,7 @@ func TestSwarmJoinTokenErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newJoinTokenCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				swarmInspectFunc: tc.swarmInspectFunc,
 				swarmUpdateFunc:  tc.swarmUpdateFunc,
 				infoFunc:         tc.infoFunc,
@@ -200,7 +200,7 @@ func TestSwarmJoinToken(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newJoinTokenCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				swarmInspectFunc: tc.swarmInspectFunc,
 				infoFunc:         tc.infoFunc,
 				nodeInspectFunc:  tc.nodeInspectFunc,

cli/command/swarm/leave_test.go

@@ -35,7 +35,7 @@ func TestSwarmLeaveErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newLeaveCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				swarmLeaveFunc: tc.swarmLeaveFunc,
 			}, buf))
 		cmd.SetArgs(tc.args)
@@ -47,7 +47,7 @@ func TestSwarmLeaveErrors(t *testing.T) {
 func TestSwarmLeave(t *testing.T) {
 	buf := new(bytes.Buffer)
 	cmd := newLeaveCommand(
-		test.NewFakeCli(&fakeClient{}, buf))
+		test.NewFakeCliWithOutput(&fakeClient{}, buf))
 	assert.NoError(t, cmd.Execute())
 	assert.Equal(t, "Node left the swarm.", strings.TrimSpace(buf.String()))
 }

cli/command/swarm/unlock_key_test.go

@@ -85,7 +85,7 @@ func TestSwarmUnlockKeyErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newUnlockKeyCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				swarmInspectFunc:      tc.swarmInspectFunc,
 				swarmUpdateFunc:       tc.swarmUpdateFunc,
 				swarmGetUnlockKeyFunc: tc.swarmGetUnlockKeyFunc,
@@ -160,7 +160,7 @@ func TestSwarmUnlockKey(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newUnlockKeyCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				swarmInspectFunc:      tc.swarmInspectFunc,
 				swarmUpdateFunc:       tc.swarmUpdateFunc,
 				swarmGetUnlockKeyFunc: tc.swarmGetUnlockKeyFunc,

cli/command/swarm/unlock_test.go

@@ -68,7 +68,7 @@ func TestSwarmUnlockErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newUnlockCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				infoFunc:        tc.infoFunc,
 				swarmUnlockFunc: tc.swarmUnlockFunc,
 			}, buf))
@@ -81,7 +81,7 @@ func TestSwarmUnlockErrors(t *testing.T) {
 func TestSwarmUnlock(t *testing.T) {
 	input := "unlockKey"
 	buf := new(bytes.Buffer)
-	dockerCli := test.NewFakeCli(&fakeClient{
+	dockerCli := test.NewFakeCliWithOutput(&fakeClient{
 		infoFunc: func() (types.Info, error) {
 			return types.Info{
 				Swarm: swarm.Info{

cli/command/swarm/update_test.go

@@ -70,7 +70,7 @@ func TestSwarmUpdateErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newUpdateCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				swarmInspectFunc:      tc.swarmInspectFunc,
 				swarmUpdateFunc:       tc.swarmUpdateFunc,
 				swarmGetUnlockKeyFunc: tc.swarmGetUnlockKeyFunc,
@@ -166,7 +166,7 @@ func TestSwarmUpdate(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newUpdateCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				swarmInspectFunc:      tc.swarmInspectFunc,
 				swarmUpdateFunc:       tc.swarmUpdateFunc,
 				swarmGetUnlockKeyFunc: tc.swarmGetUnlockKeyFunc,

cli/command/task/print_test.go

@@ -24,7 +24,7 @@ func TestTaskPrintWithQuietOption(t *testing.T) {
 	noResolve := true
 	buf := new(bytes.Buffer)
 	apiClient := &fakeClient{}
-	cli := test.NewFakeCli(apiClient, buf)
+	cli := test.NewFakeCliWithOutput(apiClient, buf)
 	tasks := []swarm.Task{
 		*Task(TaskID("id-foo")),
 	}
@@ -41,7 +41,7 @@ func TestTaskPrintWithNoTruncOption(t *testing.T) {
 	noResolve := true
 	buf := new(bytes.Buffer)
 	apiClient := &fakeClient{}
-	cli := test.NewFakeCli(apiClient, buf)
+	cli := test.NewFakeCliWithOutput(apiClient, buf)
 	tasks := []swarm.Task{
 		*Task(TaskID("id-foo-yov6omdek8fg3k5stosyp2m50")),
 	}
@@ -58,7 +58,7 @@ func TestTaskPrintWithGlobalService(t *testing.T) {
 	noResolve := true
 	buf := new(bytes.Buffer)
 	apiClient := &fakeClient{}
-	cli := test.NewFakeCli(apiClient, buf)
+	cli := test.NewFakeCliWithOutput(apiClient, buf)
 	tasks := []swarm.Task{
 		*Task(TaskServiceID("service-id-foo"), TaskNodeID("node-id-bar"), TaskSlot(0)),
 	}
@@ -75,7 +75,7 @@ func TestTaskPrintWithReplicatedService(t *testing.T) {
 	noResolve := true
 	buf := new(bytes.Buffer)
 	apiClient := &fakeClient{}
-	cli := test.NewFakeCli(apiClient, buf)
+	cli := test.NewFakeCliWithOutput(apiClient, buf)
 	tasks := []swarm.Task{
 		*Task(TaskServiceID("service-id-foo"), TaskSlot(1)),
 	}
@@ -99,7 +99,7 @@ func TestTaskPrintWithIndentation(t *testing.T) {
 			return *Node(NodeName("node-name-bar")), nil, nil
 		},
 	}
-	cli := test.NewFakeCli(apiClient, buf)
+	cli := test.NewFakeCliWithOutput(apiClient, buf)
 	tasks := []swarm.Task{
 		*Task(
 			TaskID("id-foo"),
@@ -138,7 +138,7 @@ func TestTaskPrintWithResolution(t *testing.T) {
 			return *Node(NodeName("node-name-bar")), nil, nil
 		},
 	}
-	cli := test.NewFakeCli(apiClient, buf)
+	cli := test.NewFakeCliWithOutput(apiClient, buf)
 	tasks := []swarm.Task{
 		*Task(TaskServiceID("service-id-foo"), TaskSlot(1)),
 	}

cli/command/volume/create_test.go

@@ -43,7 +43,7 @@ func TestVolumeCreateErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newCreateCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				volumeCreateFunc: tc.volumeCreateFunc,
 			}, buf),
 		)
@@ -59,7 +59,7 @@ func TestVolumeCreateErrors(t *testing.T) {
 func TestVolumeCreateWithName(t *testing.T) {
 	name := "foo"
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		volumeCreateFunc: func(body volumetypes.VolumesCreateBody) (types.Volume, error) {
 			if body.Name != name {
 				return types.Volume{}, errors.Errorf("expected name %q, got %q", name, body.Name)
@@ -97,7 +97,7 @@ func TestVolumeCreateWithFlags(t *testing.T) {
 	name := "banana"
 
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		volumeCreateFunc: func(body volumetypes.VolumesCreateBody) (types.Volume, error) {
 			if body.Name != "" {
 				return types.Volume{}, errors.Errorf("expected empty name, got %q", body.Name)

cli/command/volume/inspect_test.go

@@ -56,7 +56,7 @@ func TestVolumeInspectErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newInspectCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				volumeInspectFunc: tc.volumeInspectFunc,
 			}, buf),
 		)
@@ -98,7 +98,7 @@ func TestVolumeInspectWithoutFormat(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newInspectCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				volumeInspectFunc: tc.volumeInspectFunc,
 			}, buf),
 		)
@@ -138,7 +138,7 @@ func TestVolumeInspectWithFormat(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newInspectCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				volumeInspectFunc: tc.volumeInspectFunc,
 			}, buf),
 		)

cli/command/volume/list_test.go

@@ -39,7 +39,7 @@ func TestVolumeListErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newListCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				volumeListFunc: tc.volumeListFunc,
 			}, buf),
 		)
@@ -54,7 +54,7 @@ func TestVolumeListErrors(t *testing.T) {
 
 func TestVolumeListWithoutFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		volumeListFunc: func(filter filters.Args) (volumetypes.VolumesListOKBody, error) {
 			return volumetypes.VolumesListOKBody{
 				Volumes: []*types.Volume{
@@ -77,7 +77,7 @@ func TestVolumeListWithoutFormat(t *testing.T) {
 
 func TestVolumeListWithConfigFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		volumeListFunc: func(filter filters.Args) (volumetypes.VolumesListOKBody, error) {
 			return volumetypes.VolumesListOKBody{
 				Volumes: []*types.Volume{
@@ -102,7 +102,7 @@ func TestVolumeListWithConfigFormat(t *testing.T) {
 
 func TestVolumeListWithFormat(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cli := test.NewFakeCli(&fakeClient{
+	cli := test.NewFakeCliWithOutput(&fakeClient{
 		volumeListFunc: func(filter filters.Args) (volumetypes.VolumesListOKBody, error) {
 			return volumetypes.VolumesListOKBody{
 				Volumes: []*types.Volume{

cli/command/volume/prune_test.go

@@ -41,7 +41,7 @@ func TestVolumePruneErrors(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		cmd := NewPruneCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				volumePruneFunc: tc.volumePruneFunc,
 			}, ioutil.Discard),
 		)
@@ -70,7 +70,7 @@ func TestVolumePruneForce(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := NewPruneCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				volumePruneFunc: tc.volumePruneFunc,
 			}, buf),
 		)
@@ -88,7 +88,7 @@ func TestVolumePrunePromptYes(t *testing.T) {
 	}
 	for _, input := range []string{"y", "Y"} {
 		buf := new(bytes.Buffer)
-		cli := test.NewFakeCli(&fakeClient{
+		cli := test.NewFakeCliWithOutput(&fakeClient{
 			volumePruneFunc: simplePruneFunc,
 		}, buf)
 
@@ -110,7 +110,7 @@ func TestVolumePrunePromptNo(t *testing.T) {
 	}
 	for _, input := range []string{"n", "N", "no", "anything", "really"} {
 		buf := new(bytes.Buffer)
-		cli := test.NewFakeCli(&fakeClient{
+		cli := test.NewFakeCliWithOutput(&fakeClient{
 			volumePruneFunc: simplePruneFunc,
 		}, buf)
 

cli/command/volume/remove_test.go

@@ -31,7 +31,7 @@ func TestVolumeRemoveErrors(t *testing.T) {
 	for _, tc := range testCases {
 		buf := new(bytes.Buffer)
 		cmd := newRemoveCommand(
-			test.NewFakeCli(&fakeClient{
+			test.NewFakeCliWithOutput(&fakeClient{
 				volumeRemoveFunc: tc.volumeRemoveFunc,
 			}, buf))
 		cmd.SetArgs(tc.args)
@@ -42,7 +42,7 @@ func TestVolumeRemoveErrors(t *testing.T) {
 
 func TestNodeRemoveMultiple(t *testing.T) {
 	buf := new(bytes.Buffer)
-	cmd := newRemoveCommand(test.NewFakeCli(&fakeClient{}, buf))
+	cmd := newRemoveCommand(test.NewFakeCliWithOutput(&fakeClient{}, buf))
 	cmd.SetArgs([]string{"volume1", "volume2"})
 	assert.NoError(t, cmd.Execute())
 }

cli/internal/test/cli.go

@@ -1,6 +1,7 @@
 package test
 
 import (
+	"bytes"
 	"io"
 	"io/ioutil"
 	"strings"
@@ -16,17 +17,29 @@ type FakeCli struct {
 	client     client.APIClient
 	configfile *configfile.ConfigFile
 	out        *command.OutStream
-	err        io.Writer
+	outBuffer  *bytes.Buffer
+	err        *bytes.Buffer
 	in         *command.InStream
 	server     command.ServerInfo
 }
 
-// NewFakeCli returns a Cli backed by the fakeCli
+// NewFakeCliWithOutput returns a Cli backed by the fakeCli
-func NewFakeCli(client client.APIClient, out io.Writer) *FakeCli {
+// Deprecated: Use NewFakeCli
+func NewFakeCliWithOutput(client client.APIClient, out io.Writer) *FakeCli {
+	cli := NewFakeCli(client)
+	cli.out = command.NewOutStream(out)
+	return cli
+}
+
+// NewFakeCli returns a fake for the command.Cli interface
+func NewFakeCli(client client.APIClient) *FakeCli {
+	outBuffer := new(bytes.Buffer)
+	errBuffer := new(bytes.Buffer)
 	return &FakeCli{
 		client:     client,
-		out:        command.NewOutStream(out),
+		out:        command.NewOutStream(outBuffer),
-		err:        ioutil.Discard,
+		outBuffer:  outBuffer,
+		err:        errBuffer,
 		in:         command.NewInStream(ioutil.NopCloser(strings.NewReader(""))),
 		configfile: configfile.New("configfile"),
 	}
@@ -38,7 +51,7 @@ func (c *FakeCli) SetIn(in *command.InStream) {
 }
 
 // SetErr sets the stderr stream for the cli to the specified io.Writer
-func (c *FakeCli) SetErr(err io.Writer) {
+func (c *FakeCli) SetErr(err *bytes.Buffer) {
 	c.err = err
 }
 
@@ -76,3 +89,13 @@ func (c *FakeCli) ConfigFile() *configfile.ConfigFile {
 func (c *FakeCli) ServerInfo() command.ServerInfo {
 	return c.server
 }
+
+// OutBuffer returns the stdout buffer
+func (c *FakeCli) OutBuffer() *bytes.Buffer {
+	return c.outBuffer
+}
+
+// ErrBuffer Buffer returns the stderr buffer
+func (c *FakeCli) ErrBuffer() *bytes.Buffer {
+	return c.err
+}