stembuild: extract messenger from main()

Author: aramprice

stembuild/main.go

@@ -3,7 +3,6 @@ package main
 import (
 	"context"
 	"flag"
-	"fmt"
 	"os"
 	"path"
 	"strings"
@@ -20,18 +19,20 @@ import (
 )
 
 func main() {
+	mainMessenger := messenger.NewMainMessenger(os.Stdout, os.Stderr)
+
 	envs := os.Environ()
 	for _, env := range envs {
 		envName := strings.Split(env, "=")[0]
 		if strings.HasPrefix(envName, "GOVC_") || strings.HasPrefix(envName, "GOVMOMI_") {
-			fmt.Fprintf(os.Stderr, "Warning: The following environment variable is set and might override flags provided to stembuild: %s\n", envName) //nolint:errcheck
+			mainMessenger.EnvironmentVariableWarning(envName)
 		}
 	}
 
 	s := "./StemcellAutomation.zip"
 	err := os.WriteFile(s, assets.StemcellAutomation, 0644)
 	if err != nil {
-		fmt.Fprintln(os.Stderr, "Unable to write StemcellAutomation.zip") //nolint:errcheck
+		mainMessenger.StemcellAutomationWarning()
 		os.Exit(1)
 	}
 
@@ -66,8 +67,8 @@ func main() {
 
 	fs.Parse(os.Args[1:]) //nolint:errcheck
 	if gf.ShowVersion {
-		fmt.Fprintf(os.Stdout, "%s version %s, Windows Stemcell Building Tool\n\n", path.Base(os.Args[0]), version.Current) //nolint:errcheck
-		os.Remove(s)                                                                                                        //nolint:errcheck
+		mainMessenger.VersionInfo(path.Base(os.Args[0]), version.Current)
+		os.Remove(s) //nolint:errcheck
 		os.Exit(0)
 	}
 

stembuild/messenger/main_messenger.go

@@ -0,0 +1,27 @@
+package messenger
+
+import (
+	"fmt"
+	"io"
+)
+
+func NewMainMessenger(stdout io.Writer, stderr io.Writer) *MainMessenger {
+	return &MainMessenger{stdout: stdout, stderr: stderr}
+}
+
+type MainMessenger struct {
+	stdout io.Writer
+	stderr io.Writer
+}
+
+func (m *MainMessenger) VersionInfo(executable string, version string) {
+	write(m.stdout, fmt.Sprintf("%s version %s, Windows Stemcell Building Tool\n\n", executable, version))
+}
+
+func (m *MainMessenger) EnvironmentVariableWarning(envVarName string) {
+	write(m.stderr, fmt.Sprintf("Warning: The following environment variable is set and might override flags provided to stembuild: %s\n", envVarName))
+}
+
+func (m *MainMessenger) StemcellAutomationWarning() {
+	write(m.stderr, "Unable to write StemcellAutomation.zip")
+}

stembuild/messenger/main_messenger_test.go

@@ -0,0 +1,60 @@
+package messenger_test
+
+import (
+	"fmt"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+	. "github.com/onsi/gomega/gbytes"
+
+	"github.com/cloudfoundry/bosh-windows-stemcell-builder/stembuild/messenger"
+)
+
+var _ = Describe("MainMessenger", func() {
+	var (
+		outBuf *Buffer
+		errBuf *Buffer
+		m      *messenger.MainMessenger
+	)
+
+	BeforeEach(func() {
+		outBuf = NewBuffer()
+		errBuf = NewBuffer()
+		m = messenger.NewMainMessenger(outBuf, errBuf)
+	})
+
+	Describe("EnvironmentVariableWarning", func() {
+		It("outputs the expected warning to stderr", func() {
+			envVar := "SOME_VAR"
+			m.EnvironmentVariableWarning(envVar)
+
+			Eventually(errBuf).Should(Say(fmt.Sprintf("Warning: The following environment variable is set and might override flags provided to stembuild: %s\n", envVar)))
+		})
+	})
+
+	Describe("StemcellAutomationWarning", func() {
+		It("outputs the expected warning to stderr", func() {
+			m.StemcellAutomationWarning()
+
+			Eventually(errBuf).Should(Say("Unable to write StemcellAutomation.zip"))
+		})
+	})
+
+	Describe("StemcellAutomationWarning", func() {
+		It("outputs the expected warning to stderr", func() {
+			m.StemcellAutomationWarning()
+
+			Eventually(errBuf).Should(Say("Unable to write StemcellAutomation.zip"))
+		})
+	})
+
+	Describe("PrintVersionInfo", func() {
+		It("outputs the expected value to stdout", func() {
+			executable := "custom-stembuild"
+			version := "my.custom.version"
+			m.VersionInfo(executable, version)
+
+			Eventually(outBuf).Should(Say(fmt.Sprintf("%s version %s, Windows Stemcell Building Tool\n\n", executable, version)))
+		})
+	})
+})