diff --git a/cmd/generate/generate_test.go b/cmd/generate/generate_test.go
new file mode 100644
index 0000000..6aec68b
--- /dev/null
+++ b/cmd/generate/generate_test.go
@@ -0,0 +1,102 @@
+package generate
+
+import (
+	"codegen/internal/flagkeys"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+
+	"github.com/spf13/afero"
+	"github.com/spf13/viper"
+)
+
+func TestGenerateGoSuccess(t *testing.T) {
+	// Constant paths.
+	const memoryManifestPath = "manifest/path.json"
+	const memoryOutputPath = "output/path.go"
+	const packageName = "testpackage"
+	const testFileManifest = "testdata/success_manifest.golden"
+	const testFileGo = "testdata/success_go.golden"
+
+	// Prepare in-memory files.
+	fs := afero.NewMemMapFs()
+	viper.Set(flagkeys.FileSystem, fs)
+	readOsFileAndWriteToMemMap(t, testFileManifest, memoryManifestPath, fs)
+
+	// Prepare command.
+	Root.SetArgs([]string{"go",
+		"--flag_manifest_path", memoryManifestPath,
+		"--output_path", memoryOutputPath,
+		"--package_name", packageName,
+	})
+
+	// Run command.
+	Root.Execute()
+
+	// Compare result.
+	compareOutput(t, testFileGo, memoryOutputPath, fs)
+}
+
+func TestGenerateReactSuccess(t *testing.T) {
+	// Constant paths.
+	const memoryManifestPath = "manifest/path.json"
+	const memoryOutputPath = "output/path.ts"
+	const testFileManifest = "testdata/success_manifest.golden"
+	const testFileReact = "testdata/success_react.golden"
+
+	// Prepare in-memory files.
+	fs := afero.NewMemMapFs()
+	viper.Set(flagkeys.FileSystem, fs)
+	readOsFileAndWriteToMemMap(t, testFileManifest, memoryManifestPath, fs)
+
+	// Prepare command.
+	Root.SetArgs([]string{"react",
+		"--flag_manifest_path", memoryManifestPath,
+		"--output_path", memoryOutputPath,
+	})
+
+	// Run command.
+	Root.Execute()
+
+	// Compare result.
+	compareOutput(t, testFileReact, memoryOutputPath, fs)
+}
+
+func readOsFileAndWriteToMemMap(t *testing.T, inputPath string, memPath string, memFs afero.Fs) {
+	data, err := os.ReadFile(inputPath)
+	if err != nil {
+		t.Fatalf("error reading file %q: %v", inputPath, err)
+	}
+	if err := memFs.MkdirAll(filepath.Dir(memPath), 0660); err != nil {
+		t.Fatalf("error creating directory %q: %v", filepath.Dir(memPath), err)
+	}
+	f, err := memFs.Create(memPath)
+	if err != nil {
+		t.Fatalf("error creating file %q: %v", memPath, err)
+	}
+	defer f.Close()
+	writtenBytes, err := f.Write(data)
+	if err != nil {
+		t.Fatalf("error writing contents to file %q: %v", memPath, err)
+	}
+	if writtenBytes != len(data) {
+		t.Fatalf("error writing entire file %v: writtenBytes != expectedWrittenBytes", memPath)
+	}
+}
+
+func compareOutput(t *testing.T, testFile, memoryOutputPath string, fs afero.Fs) {
+	want, err := os.ReadFile(testFile)
+	if err != nil {
+		t.Fatalf("error reading file %q: %v", testFile, err)
+
+	}
+	got, err := afero.ReadFile(fs, memoryOutputPath)
+	if err != nil {
+		t.Fatalf("error reading file %q: %v", memoryOutputPath, err)
+	}
+	if diff := cmp.Diff(want, got); diff != "" {
+		t.Errorf("output mismatch (-want +got):\n%s", diff)
+	}
+}
diff --git a/cmd/generate/testdata/success_go.golden b/cmd/generate/testdata/success_go.golden
new file mode 100644
index 0000000..ccf281e
--- /dev/null
+++ b/cmd/generate/testdata/success_go.golden
@@ -0,0 +1,49 @@
+package testpackage
+
+import (
+	"context"
+	"github.com/open-feature/go-sdk/openfeature"
+)
+
+type BooleanProvider func(ctx context.Context) (bool, error)
+type FloatProvider func(ctx context.Context) (float64, error)
+type IntProvider func(ctx context.Context) (int64, error)
+type StringProvider func(ctx context.Context) (string, error)
+
+var client *openfeature.Client = nil
+// Discount percentage applied to purchases.
+var DiscountPercentage = struct {
+    Value FloatProvider
+}{
+    Value: func(ctx context.Context) (float64, error) {
+        return client.FloatValue(ctx, "discountPercentage", 0.15, openfeature.EvaluationContext{})
+    },
+}
+// Controls whether Feature A is enabled.
+var EnableFeatureA = struct {
+    Value BooleanProvider
+}{
+    Value: func(ctx context.Context) (bool, error) {
+        return client.BooleanValue(ctx, "enableFeatureA", false, openfeature.EvaluationContext{})
+    },
+}
+// The message to use for greeting users.
+var GreetingMessage = struct {
+    Value StringProvider
+}{
+    Value: func(ctx context.Context) (string, error) {
+        return client.StringValue(ctx, "greetingMessage", "Hello there!", openfeature.EvaluationContext{})
+    },
+}
+// Maximum allowed length for usernames.
+var UsernameMaxLength = struct {
+    Value IntProvider
+}{
+    Value: func(ctx context.Context) (int64, error) {
+        return client.IntValue(ctx, "usernameMaxLength", 50, openfeature.EvaluationContext{})
+    },
+}
+
+func init() {
+	client = openfeature.NewClient("testpackage")
+}
diff --git a/cmd/generate/testdata/success_manifest.golden b/cmd/generate/testdata/success_manifest.golden
new file mode 100644
index 0000000..2df98b6
--- /dev/null
+++ b/cmd/generate/testdata/success_manifest.golden
@@ -0,0 +1,32 @@
+{
+    "flags": {
+      "enableFeatureA": {
+        "flagType": "boolean",
+        "defaultValue": false,
+        "description": "Controls whether Feature A is enabled."
+      },
+      "usernameMaxLength": {
+        "flagType": "integer",
+        "defaultValue": 50,
+        "description": "Maximum allowed length for usernames."
+      },
+      "greetingMessage": {
+        "flagType": "string",
+        "defaultValue": "Hello there!",
+        "description": "The message to use for greeting users."
+      },
+      "discountPercentage": {
+        "flagType": "float",
+        "defaultValue": 0.15,
+        "description": "Discount percentage applied to purchases."
+      },
+      "themeCustomization": {
+        "flagType": "object",
+        "defaultValue": {
+          "primaryColor": "#007bff",
+          "secondaryColor": "#6c757d"
+        },
+        "description": "Allows customization of theme colors."
+      }
+    }
+  }
\ No newline at end of file
diff --git a/cmd/generate/testdata/success_react.golden b/cmd/generate/testdata/success_react.golden
new file mode 100644
index 0000000..9a68ec5
--- /dev/null
+++ b/cmd/generate/testdata/success_react.golden
@@ -0,0 +1,55 @@
+'use client';
+
+import {
+	useBooleanFlagDetails,
+	useNumberFlagDetails,
+	useStringFlagDetails,
+} from "@openfeature/react-sdk";
+
+/**
+* Discount percentage applied to purchases.
+* 
+* **Details:**
+* - flag key: `discountPercentage`
+* - default value: `0.15`
+* - type: `number`
+*/
+export const useDiscountPercentage = (options: Parameters<typeof useNumberFlagDetails>[2]) => {
+  return useNumberFlagDetails("discountPercentage", 0.15, options);
+};
+
+/**
+* Controls whether Feature A is enabled.
+* 
+* **Details:**
+* - flag key: `enableFeatureA`
+* - default value: `false`
+* - type: `boolean`
+*/
+export const useEnableFeatureA = (options: Parameters<typeof useBooleanFlagDetails>[2]) => {
+  return useBooleanFlagDetails("enableFeatureA", false, options);
+};
+
+/**
+* The message to use for greeting users.
+* 
+* **Details:**
+* - flag key: `greetingMessage`
+* - default value: `Hello there!`
+* - type: `string`
+*/
+export const useGreetingMessage = (options: Parameters<typeof useStringFlagDetails>[2]) => {
+  return useStringFlagDetails("greetingMessage", "Hello there!", options);
+};
+
+/**
+* Maximum allowed length for usernames.
+* 
+* **Details:**
+* - flag key: `usernameMaxLength`
+* - default value: `50`
+* - type: `number`
+*/
+export const useUsernameMaxLength = (options: Parameters<typeof useNumberFlagDetails>[2]) => {
+  return useNumberFlagDetails("usernameMaxLength", 50, options);
+};
diff --git a/go.mod b/go.mod
index de23b4e..97d9d17 100644
--- a/go.mod
+++ b/go.mod
@@ -32,6 +32,7 @@ require (
 
 require (
 	github.com/go-logr/logr v1.4.2 // indirect
+	github.com/google/go-cmp v0.6.0
 	github.com/spf13/cobra v1.8.1
 	github.com/spf13/viper v1.19.0
 	golang.org/x/exp v0.0.0-20240506185415-9bf2ced13842 // indirect
diff --git a/go.sum b/go.sum
index 39f15cf..acfce07 100644
--- a/go.sum
+++ b/go.sum
@@ -7,6 +7,8 @@ github.com/go-logr/logr v1.4.2 h1:6pFjapn8bFcIbiKo3XT4j/BhANplGihG6tvd+8rYgrY=
 github.com/go-logr/logr v1.4.2/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
 github.com/golang/mock v1.6.0 h1:ErTB+efbowRARo13NNdxyJji2egdxLGQhRaY+DUumQc=
 github.com/golang/mock v1.6.0/go.mod h1:p6yTPP+5HYm5mzsMV8JkE6ZKdX+/wYM6Hr+LicevLPs=
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/hashicorp/hcl v1.0.0 h1:0Anlzjpi4vEasTeNFn2mLJgTSwt0+6sfsiTG8qcWGx4=
 github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T20WEQ=
 github.com/iancoleman/strcase v0.3.0 h1:nTXanmYxhfFAMjZL34Ov6gkzEsSJZ5DbhxWjvSASxEI=
diff --git a/internal/filesystem/filesystem.go b/internal/filesystem/filesystem.go
new file mode 100644
index 0000000..b2e8e6a
--- /dev/null
+++ b/internal/filesystem/filesystem.go
@@ -0,0 +1,17 @@
+// Package filesystem contains the filesystem interface.
+package filesystem
+
+import (
+	"codegen/internal/flagkeys"
+
+	"github.com/spf13/afero"
+	"github.com/spf13/viper"
+)
+
+func FileSystem() afero.Fs {
+	return viper.Get(flagkeys.FileSystem).(afero.Fs)
+}
+
+func init() {
+	viper.SetDefault(flagkeys.FileSystem, afero.NewOsFs())
+}
diff --git a/internal/flagkeys/flagkeys.go b/internal/flagkeys/flagkeys.go
index 61d8518..90f1976 100644
--- a/internal/flagkeys/flagkeys.go
+++ b/internal/flagkeys/flagkeys.go
@@ -1,6 +1,8 @@
 // Package commonflags contains keys for all command-line flags related to openfeature CLI.
 package flagkeys
 
+import "github.com/spf13/viper"
+
 const (
 	// `generate` flags:
 	// FlagManifestPath is the key for the flag that stores the flag manifest path.
@@ -11,4 +13,12 @@ const (
 	// `generate go` flags:
 	// GoPackageName is the key for the flag that stores the Golang package name.
 	GoPackageName = "package_name"
+
+	//internal keys:
+	// FileSystem is the key for the flag that stores the filesystem interface.
+	FileSystem = "filesystem"
 )
+
+func init() {
+	viper.SetDefault(FileSystem, "local")
+}
diff --git a/internal/generate/generate.go b/internal/generate/generate.go
index c7b3d97..e92d2c5 100644
--- a/internal/generate/generate.go
+++ b/internal/generate/generate.go
@@ -3,11 +3,11 @@ package generate
 
 import (
 	"bytes"
+	"codegen/internal/filesystem"
 	"codegen/internal/flagkeys"
 	"codegen/internal/generate/manifestutils"
 	"codegen/internal/generate/types"
 	"fmt"
-	"os"
 	"path"
 	"path/filepath"
 	"text/template"
@@ -28,10 +28,11 @@ func GenerateFile(funcs template.FuncMap, contents string, data types.TmplDataIn
 		return fmt.Errorf("error executing template: %v", err)
 	}
 	outputPath := data.BaseTmplDataInfo().OutputPath
-	if err := os.MkdirAll(filepath.Dir(outputPath), 0770); err != nil {
+	fs := filesystem.FileSystem()
+	if err := fs.MkdirAll(filepath.Dir(outputPath), 0660); err != nil {
 		return err
 	}
-	f, err := os.Create(path.Join(outputPath))
+	f, err := fs.Create(path.Join(outputPath))
 	if err != nil {
 		return fmt.Errorf("error creating file %q: %v", outputPath, err)
 	}
diff --git a/internal/generate/manifestutils/manifestutils.go b/internal/generate/manifestutils/manifestutils.go
index ac19db0..3ef464d 100644
--- a/internal/generate/manifestutils/manifestutils.go
+++ b/internal/generate/manifestutils/manifestutils.go
@@ -3,20 +3,23 @@ package manifestutils
 
 import (
 	flagmanifest "codegen/docs/schema/v0"
+	"codegen/internal/filesystem"
 	"codegen/internal/flagkeys"
 	"codegen/internal/generate/types"
 	"encoding/json"
 	"fmt"
-	"os"
+	"sort"
 	"strconv"
 
 	"github.com/santhosh-tekuri/jsonschema/v5"
+	"github.com/spf13/afero"
 	"github.com/spf13/viper"
 )
 
 // LoadData loads the data from the flag manifest.
 func LoadData(manifestPath string, supportedFlagTypes map[types.FlagType]bool) (*types.BaseTmplData, error) {
-	data, err := os.ReadFile(manifestPath)
+	fs := filesystem.FileSystem()
+	data, err := afero.ReadFile(fs, manifestPath)
 	if err != nil {
 		return nil, fmt.Errorf("error reading contents from file %q", manifestPath)
 	}
@@ -101,5 +104,9 @@ func unmarshalFlagManifest(data []byte) (*types.BaseTmplData, error) {
 			Docs:         docs,
 		})
 	}
+	// Ensure consistency of order of flag generation.
+	sort.Slice(btData.Flags, func(i, j int) bool {
+		return btData.Flags[i].Name < btData.Flags[j].Name
+	})
 	return &btData, nil
 }
diff --git a/internal/testutils/testutils.go b/internal/testutils/testutils.go
new file mode 100644
index 0000000..95c4dc9
--- /dev/null
+++ b/internal/testutils/testutils.go
@@ -0,0 +1 @@
+package testutils
diff --git a/main.go b/main.go
index b7bd958..f6d681d 100644
--- a/main.go
+++ b/main.go
@@ -4,9 +4,9 @@ import "codegen/cmd"
 
 var (
 	// Overridden by Go Releaser at build time
-	version    = "dev"
-	commit     = "HEAD"
-	date       = "unknown"
+	version = "dev"
+	commit  = "HEAD"
+	date    = "unknown"
 )
 
 func main() {