From 3e7f1a0a7f1858f280af35419eef36c1730daddf Mon Sep 17 00:00:00 2001
From: Fabian Vowie <fabian@vowie.me>
Date: Mon, 17 Jan 2022 17:01:54 +0100
Subject: [PATCH] Improve testability for LoadSettings function

---
 main.go                   |  3 ++-
 settings/settings.go      |  8 +++++---
 settings/settings_test.go | 24 +++++++++++++++++++++++-
 3 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/main.go b/main.go
index e8bf674..ea60a8f 100644
--- a/main.go
+++ b/main.go
@@ -8,6 +8,7 @@ import (
 	"github.com/geplauder/lithium/settings"
 	"github.com/geplauder/lithium/storage"
 	"github.com/gorilla/mux"
+	"github.com/spf13/afero"
 )
 
 const Name string = "Lithium"
@@ -43,7 +44,7 @@ func RegisterPipelineRoutes(r *mux.Router, pipelines []pipelines.IPipeline, stor
 }
 
 func main() {
-	settings := settings.LoadSettings()
+	settings := settings.LoadSettings(afero.NewOsFs())
 
 	var storageProvider storage.IStorageProvider
 
diff --git a/settings/settings.go b/settings/settings.go
index 35e960d..b0006b1 100644
--- a/settings/settings.go
+++ b/settings/settings.go
@@ -4,6 +4,8 @@ import (
 	"encoding/json"
 	"os"
 	"path/filepath"
+
+	"github.com/spf13/afero"
 )
 
 const (
@@ -31,12 +33,12 @@ func parseSettings(data []byte) Settings {
 	return settings
 }
 
-func LoadSettings() Settings {
+func LoadSettings(fileSystem afero.Fs) Settings {
 	workingDirectory, _ := os.Getwd()
 	path := filepath.Join(workingDirectory, "settings.json")
 
 	// Load file and parse file
-	data, err := os.ReadFile(path)
+	data, err := afero.ReadFile(fileSystem, path)
 
 	if err == nil {
 		return parseSettings(data)
@@ -53,7 +55,7 @@ func LoadSettings() Settings {
 	}
 
 	serializedSettings, err := json.MarshalIndent(defaultSettings, "", "\t")
-	os.WriteFile(path, serializedSettings, os.ModePerm)
+	afero.WriteFile(fileSystem, path, serializedSettings, os.ModePerm)
 
 	return defaultSettings
 }
diff --git a/settings/settings_test.go b/settings/settings_test.go
index 96e667a..2610eab 100644
--- a/settings/settings_test.go
+++ b/settings/settings_test.go
@@ -1,12 +1,15 @@
 package settings
 
 import (
+	"os"
+	"path/filepath"
 	"testing"
 
+	"github.com/spf13/afero"
 	"github.com/stretchr/testify/assert"
 )
 
-func TestSettingsLoading(t *testing.T) {
+func TestSettingsParsing(t *testing.T) {
 	const file string = `{
 		"endpoint": "0.0.0.0:8000",
 		"token": "foobar",
@@ -24,3 +27,22 @@ func TestSettingsLoading(t *testing.T) {
 		assert.Equal(t, "assets", settings.StorageProvider.BasePath)
 	})
 }
+
+func TestSettingsLoading(t *testing.T) {
+	t.Run("Settings loading creates default settings.json when none is present", func(t *testing.T) {
+		fileSystem := afero.NewMemMapFs()
+		workingDirectory, _ := os.Getwd()
+
+		path := filepath.Join(workingDirectory, "settings.json")
+
+		// Settings file does not exist in the beginning
+		doesFileExist, _ := afero.Exists(fileSystem, path)
+		assert.False(t, doesFileExist)
+
+		LoadSettings(fileSystem)
+
+		// Settings file should be present after calling LoadSettings
+		doesFileExist, _ = afero.Exists(fileSystem, path)
+		assert.True(t, doesFileExist)
+	})
+}