Unit test localproject.Write

Refactored Write to separate IO functionality from main caller, for
easier testing

ecs-cli/modules/cli/local/project/project.go

@@ -163,40 +163,52 @@ func (p *localProject) Convert() error {
 func (p *localProject) Write() error {
 	// Will error if the file already exists, otherwise create
 
-	outputFileName := p.context.String(flags.LocalOutputFlag)
-	if outputFileName == "" {
-		outputFileName = LocalOutDefaultFileName
+	p.localOutFileName = LocalOutDefaultFileName
+	if fileName := p.context.String(flags.LocalOutputFlag); fileName != "" {
+		p.localOutFileName = fileName
 	}
-	p.localOutFileName = outputFileName
 
-	out, err := os.OpenFile(outputFileName, os.O_WRONLY|os.O_CREATE|os.O_EXCL, LocalOutFileMode)
-	defer out.Close()
+	return p.writeFile()
+}
 
-	data := p.localBytes
+func (p *localProject) writeFile() error {
+	out, err := openFile(p.localOutFileName)
+	defer out.Close()
 
+	// File already exists
 	if err != nil {
-		fmt.Printf("%s file already exists. Do you want to write over this file? [y/N]\n", outputFileName)
+		return p.overwriteFile()
+	}
 
-		reader := bufio.NewReader(os.Stdin)
-		input, err := reader.ReadString('\n')
-		if err != nil {
-			return fmt.Errorf("Error reading input: %s", err.Error())
-		}
+	_, err = out.Write(p.localBytes)
 
-		formattedInput := strings.ToLower(strings.TrimSpace(input))
+	return err
+}
 
-		if formattedInput != "yes" && formattedInput != "y" {
-			return fmt.Errorf("Aborted writing compose file. To retry, rename or move %s", outputFileName) // TODO add force flag
-		}
+// Facilitates test mocking
+var openFile func(filename string) (*os.File, error) = func(filename string) (*os.File, error) {
+	return os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_EXCL, LocalOutFileMode)
+}
 
-		// Overwrite local compose file
-		err = ioutil.WriteFile(outputFileName, data, LocalOutFileMode)
-		return err
+func (p *localProject) overwriteFile() error {
+	filename := p.localOutFileName
+
+	fmt.Printf("%s file already exists. Do you want to write over this file? [y/N]\n", filename)
+
+	reader := bufio.NewReader(os.Stdin)
+	stdin, err := reader.ReadString('\n')
+	if err != nil {
+		return fmt.Errorf("Error reading stdin: %s", err.Error())
 	}
 
-	_, err = out.Write(data)
+	input := strings.ToLower(strings.TrimSpace(stdin))
 
-	return err
+	if input != "yes" && input != "y" {
+		return fmt.Errorf("Aborted writing compose file. To retry, rename or move %s", filename) // TODO add force flag
+	}
+
+	// Overwrite local compose file
+	return ioutil.WriteFile(filename, p.localBytes, LocalOutFileMode)
 }
 
 // Get secret value stored in AWS Secrets Manager

ecs-cli/modules/cli/local/project/project_test.go

@@ -0,0 +1,78 @@
+// Copyright 2015-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"). You may
+// not use this file except in compliance with the License. A copy of the
+// License is located at
+//
+//	http://aws.amazon.com/apache2.0/
+//
+// or in the "license" file accompanying this file. This file 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 localproject defines LocalProject interface and implements them on localProject
+
+package localproject
+
+import (
+	"flag"
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/aws/amazon-ecs-cli/ecs-cli/modules/commands/flags"
+	"github.com/stretchr/testify/assert"
+	"github.com/urfave/cli"
+)
+
+func TestWrite(t *testing.T) {
+	// GIVEN
+	flagSet := flag.NewFlagSet("ecs-cli", 0) // No flags specified
+	context := cli.NewContext(nil, flagSet, nil)
+	project := New(context)
+
+	oldOpenFile := openFile
+	openFile = func(filename string) (*os.File, error) {
+		tmpfile, err := ioutil.TempFile("", filename)
+		assert.NoError(t, err, "Unexpected error in creating temp compose file")
+		defer os.Remove(tmpfile.Name())
+
+		return tmpfile, nil
+	}
+	defer func() { openFile = oldOpenFile }()
+
+	// WHEN
+	err := project.Write()
+
+	// THEN
+	assert.NoError(t, err, "Unexpected error in writing local compose file")
+	assert.Equal(t, LocalOutDefaultFileName, project.LocalOutFileName())
+}
+
+func TestWrite_WithOutputFlag(t *testing.T) {
+	// GIVEN
+	expectedOutputFile := "foo.yml"
+	flagSet := flag.NewFlagSet("ecs-cli", 0)
+	flagSet.String(flags.LocalOutputFlag, expectedOutputFile, "")
+	context := cli.NewContext(nil, flagSet, nil)
+	project := New(context)
+
+	oldOpenFile := openFile
+	openFile = func(filename string) (*os.File, error) {
+		tmpfile, err := ioutil.TempFile("", filename)
+		assert.NoError(t, err, "Unexpected error in creating temp compose file")
+		defer os.Remove(tmpfile.Name())
+
+		return tmpfile, nil
+	}
+
+	defer func() { openFile = oldOpenFile }()
+
+	// WHEN
+	err := project.Write()
+
+	// THEN
+	assert.NoError(t, err, "Unexpected error in writing local compose file")
+	assert.Equal(t, expectedOutputFile, project.LocalOutFileName())
+}