refactor(fixer.go): rename rewrite to replaceLines for clarity

feat(fixer.go): extract writeFile function for better code organization
test(main_test.go): rename TestGolden to TestMainGolden for specificity
refactor(main_test.go): use variable for file paths to reduce duplication
feat(main_test.go): add checkContent function to compare file contents directly

fixer.go

@@ -22,7 +22,7 @@ func fix(filename, functionName string) error {
 		return err
 	}
 
-	if err := rewrite(filename, start, end); err != nil {
+	if err := replaceLines(filename, start, end); err != nil {
 		return err
 	}
 	return nil
@@ -74,7 +74,7 @@ func lookup(filename, functionName string) (int, int, error) {
 	return start, end, nil
 }
 
-func rewrite(filename string, start, end int) error {
+func replaceLines(filename string, start, end int) error {
 	file, err := os.Open(filename)
 	if err != nil {
 		return err
@@ -100,12 +100,17 @@ func rewrite(filename string, start, end int) error {
 	if err != nil {
 		return err
 	}
+	// write to file
+	return writeFile(file, b)
+}
+
+func writeFile(file *os.File, b []byte) error {
 	// write to file
 	info, err := file.Stat()
 	if err != nil {
 		return err
 	}
-	if err := os.WriteFile(filename, b, info.Mode()); err != nil {
+	if err := os.WriteFile(file.Name(), b, info.Mode()); err != nil {
 		return err
 	}
 	return nil

main_test.go

@@ -8,19 +8,18 @@ import (
 	"rsc.io/script"
 )
 
-func TestGolden(t *testing.T) {
+func TestMainGolden(t *testing.T) {
 	ctx := context.Background()
 	state, err := script.NewState(ctx, "./", nil)
 	if err != nil {
 		t.Fatal(err)
 	}
-	_, err = script.Cp().Run(state, "testdata/main.go", "testdata/main.go.backup")
-	if err != nil {
+	mainFile := "testdata/main.go"
+	if _, err := script.Cp().Run(state, mainFile, mainFile+".backup"); err != nil {
 		t.Fatal(err)
 	}
 	defer func() {
-		_, err = script.Mv().Run(state, "testdata/main.go.backup", "testdata/main.go")
-		if err != nil {
+		if _, err := script.Mv().Run(state, mainFile+".backup", mainFile); err != nil {
 			t.Fatal(err)
 		}
 	}()
@@ -34,9 +33,21 @@ func TestGolden(t *testing.T) {
 	os.Stdin = f
 	main()
 
-	got, err := os.Stat("testdata/main.go")
-	expected, err := os.Stat("testdata/main.go.golden")
-	if !os.SameFile(got, expected) {
-		t.Errorf("unexpected file content")
+	checkContent(t, mainFile, mainFile+".golden")
+}
+
+func checkContent(t *testing.T, f1, f2 string) {
+	t.Helper()
+
+	got, err := os.ReadFile(f1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	expected, err := os.ReadFile(f2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != string(expected) {
+		t.Errorf("got %s, expected %s", got, expected)
 	}
 }