test(locale): increase test coverage to 100%

internal/locale/error_test.go

@@ -0,0 +1,279 @@
+// SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package locale // import "miniflux.app/v2/internal/locale"
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestNewLocalizedErrorWrapper(t *testing.T) {
+	originalErr := errors.New("original error message")
+	translationKey := "error.test_key"
+	args := []any{"arg1", 42}
+
+	wrapper := NewLocalizedErrorWrapper(originalErr, translationKey, args...)
+
+	if wrapper.originalErr != originalErr {
+		t.Errorf("Expected original error to be %v, got %v", originalErr, wrapper.originalErr)
+	}
+
+	if wrapper.translationKey != translationKey {
+		t.Errorf("Expected translation key to be %q, got %q", translationKey, wrapper.translationKey)
+	}
+
+	if len(wrapper.translationArgs) != 2 {
+		t.Errorf("Expected 2 translation args, got %d", len(wrapper.translationArgs))
+	}
+
+	if wrapper.translationArgs[0] != "arg1" || wrapper.translationArgs[1] != 42 {
+		t.Errorf("Expected translation args [arg1, 42], got %v", wrapper.translationArgs)
+	}
+}
+
+func TestLocalizedErrorWrapper_Error(t *testing.T) {
+	originalErr := errors.New("original error message")
+	wrapper := NewLocalizedErrorWrapper(originalErr, "error.test_key")
+
+	result := wrapper.Error()
+	if result != originalErr {
+		t.Errorf("Expected Error() to return original error %v, got %v", originalErr, result)
+	}
+}
+
+func TestLocalizedErrorWrapper_Translate(t *testing.T) {
+	// Set up test catalog
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"error.test_key": "Error: %s (code: %d)",
+		},
+		"fr_FR": translationDict{
+			"error.test_key": "Erreur : %s (code : %d)",
+		},
+	}
+
+	originalErr := errors.New("original error")
+	wrapper := NewLocalizedErrorWrapper(originalErr, "error.test_key", "test message", 404)
+
+	// Test English translation
+	result := wrapper.Translate("en_US")
+	expected := "Error: test message (code: 404)"
+	if result != expected {
+		t.Errorf("Expected English translation %q, got %q", expected, result)
+	}
+
+	// Test French translation
+	result = wrapper.Translate("fr_FR")
+	expected = "Erreur : test message (code : 404)"
+	if result != expected {
+		t.Errorf("Expected French translation %q, got %q", expected, result)
+	}
+
+	// Test with missing language (should use key as fallback with args applied)
+	result = wrapper.Translate("invalid_lang")
+	expected = "error.test_key%!(EXTRA string=test message, int=404)"
+	if result != expected {
+		t.Errorf("Expected fallback translation %q, got %q", expected, result)
+	}
+}
+
+func TestLocalizedErrorWrapper_TranslateWithEmptyKey(t *testing.T) {
+	originalErr := errors.New("original error message")
+	wrapper := NewLocalizedErrorWrapper(originalErr, "")
+
+	result := wrapper.Translate("en_US")
+	expected := "original error message"
+	if result != expected {
+		t.Errorf("Expected original error message %q, got %q", expected, result)
+	}
+}
+
+func TestLocalizedErrorWrapper_TranslateWithNoArgs(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"error.simple": "Simple error message",
+		},
+	}
+
+	originalErr := errors.New("original error")
+	wrapper := NewLocalizedErrorWrapper(originalErr, "error.simple")
+
+	result := wrapper.Translate("en_US")
+	expected := "Simple error message"
+	if result != expected {
+		t.Errorf("Expected translation %q, got %q", expected, result)
+	}
+}
+
+func TestNewLocalizedError(t *testing.T) {
+	translationKey := "error.validation"
+	args := []any{"field1", "invalid"}
+
+	localizedErr := NewLocalizedError(translationKey, args...)
+
+	if localizedErr.translationKey != translationKey {
+		t.Errorf("Expected translation key to be %q, got %q", translationKey, localizedErr.translationKey)
+	}
+
+	if len(localizedErr.translationArgs) != 2 {
+		t.Errorf("Expected 2 translation args, got %d", len(localizedErr.translationArgs))
+	}
+
+	if localizedErr.translationArgs[0] != "field1" || localizedErr.translationArgs[1] != "invalid" {
+		t.Errorf("Expected translation args [field1, invalid], got %v", localizedErr.translationArgs)
+	}
+}
+
+func TestLocalizedError_String(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"error.validation": "Validation failed for %s: %s",
+		},
+	}
+
+	localizedErr := NewLocalizedError("error.validation", "username", "too short")
+
+	result := localizedErr.String()
+	expected := "Validation failed for username: too short"
+	if result != expected {
+		t.Errorf("Expected String() result %q, got %q", expected, result)
+	}
+}
+
+func TestLocalizedError_StringWithMissingTranslation(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{},
+	}
+
+	localizedErr := NewLocalizedError("error.missing", "arg1")
+
+	result := localizedErr.String()
+	expected := "error.missing%!(EXTRA string=arg1)"
+	if result != expected {
+		t.Errorf("Expected String() result %q, got %q", expected, result)
+	}
+}
+
+func TestLocalizedError_Error(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"error.database": "Database connection failed: %s",
+		},
+	}
+
+	localizedErr := NewLocalizedError("error.database", "timeout")
+
+	result := localizedErr.Error()
+	if result == nil {
+		t.Error("Expected Error() to return a non-nil error")
+	}
+
+	expected := "Database connection failed: timeout"
+	if result.Error() != expected {
+		t.Errorf("Expected Error() message %q, got %q", expected, result.Error())
+	}
+}
+
+func TestLocalizedError_Translate(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"error.permission": "Permission denied for %s",
+		},
+		"es_ES": translationDict{
+			"error.permission": "Permiso denegado para %s",
+		},
+	}
+
+	localizedErr := NewLocalizedError("error.permission", "admin panel")
+
+	// Test English translation
+	result := localizedErr.Translate("en_US")
+	expected := "Permission denied for admin panel"
+	if result != expected {
+		t.Errorf("Expected English translation %q, got %q", expected, result)
+	}
+
+	// Test Spanish translation
+	result = localizedErr.Translate("es_ES")
+	expected = "Permiso denegado para admin panel"
+	if result != expected {
+		t.Errorf("Expected Spanish translation %q, got %q", expected, result)
+	}
+
+	// Test with missing language
+	result = localizedErr.Translate("invalid_lang")
+	expected = "error.permission%!(EXTRA string=admin panel)"
+	if result != expected {
+		t.Errorf("Expected fallback translation %q, got %q", expected, result)
+	}
+}
+
+func TestLocalizedError_TranslateWithNoArgs(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"error.generic": "An error occurred",
+		},
+		"de_DE": translationDict{
+			"error.generic": "Ein Fehler ist aufgetreten",
+		},
+	}
+
+	localizedErr := NewLocalizedError("error.generic")
+
+	// Test English
+	result := localizedErr.Translate("en_US")
+	expected := "An error occurred"
+	if result != expected {
+		t.Errorf("Expected English translation %q, got %q", expected, result)
+	}
+
+	// Test German
+	result = localizedErr.Translate("de_DE")
+	expected = "Ein Fehler ist aufgetreten"
+	if result != expected {
+		t.Errorf("Expected German translation %q, got %q", expected, result)
+	}
+}
+
+func TestLocalizedError_TranslateWithComplexArgs(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"error.complex": "Error %d: %s occurred at %s with severity %s",
+		},
+	}
+
+	localizedErr := NewLocalizedError("error.complex", 500, "Internal Server Error", "2024-01-01", "high")
+
+	result := localizedErr.Translate("en_US")
+	expected := "Error 500: Internal Server Error occurred at 2024-01-01 with severity high"
+	if result != expected {
+		t.Errorf("Expected complex translation %q, got %q", expected, result)
+	}
+}
+
+func TestLocalizedErrorWrapper_WithNilError(t *testing.T) {
+	// This tests edge case behavior - what happens with nil error
+	wrapper := NewLocalizedErrorWrapper(nil, "error.test")
+
+	// Error() should return nil
+	result := wrapper.Error()
+	if result != nil {
+		t.Errorf("Expected Error() to return nil, got %v", result)
+	}
+}
+
+func TestLocalizedError_EmptyKey(t *testing.T) {
+	localizedErr := NewLocalizedError("")
+
+	result := localizedErr.String()
+	expected := ""
+	if result != expected {
+		t.Errorf("Expected empty string for empty key, got %q", result)
+	}
+
+	result = localizedErr.Translate("en_US")
+	if result != expected {
+		t.Errorf("Expected empty string for empty key translation, got %q", result)
+	}
+}

internal/locale/plural_test.go

@@ -7,84 +7,192 @@ import "testing"
 
 func TestPluralRules(t *testing.T) {
 	scenarios := map[string]map[int]int{
+		// Default rule (covers fr_FR, pt_BR, tr_TR, and other unlisted languages)
 		"default": {
-			1: 0,
-			2: 1,
-			5: 1,
+			0: 0, // n <= 1
+			1: 0, // n <= 1
+			2: 1, // n > 1
+			5: 1, // n > 1
 		},
+		// Arabic (ar_AR) - 6 forms
 		"ar_AR": {
-			0:   0,
-			1:   1,
-			2:   2,
-			5:   3,
-			11:  4,
-			200: 5,
-		},
+			0:   0, // n == 0
+			1:   1, // n == 1
+			2:   2, // n == 2
+			3:   3, // n%100 >= 3 && n%100 <= 10
+			5:   3, // n%100 >= 3 && n%100 <= 10
+			10:  3, // n%100 >= 3 && n%100 <= 10
+			11:  4, // n%100 >= 11
+			15:  4, // n%100 >= 11
+			99:  4, // n%100 >= 11
+			100: 5, // default case (n%100 == 0, doesn't match any condition)
+			101: 5, // default case (n%100 == 1, but n != 1)
+			200: 5, // default case
+		},
+		// Czech (cs_CZ) - 3 forms
 		"cs_CZ": {
-			1: 0,
-			2: 1,
-			5: 2,
+			1: 0, // n == 1
+			2: 1, // n >= 2 && n <= 4
+			3: 1, // n >= 2 && n <= 4
+			4: 1, // n >= 2 && n <= 4
+			5: 2, // default case
 		},
+		// French (fr_FR) - uses default rule
 		"fr_FR": {
-			1: 0,
-			2: 1,
-			5: 1,
+			0: 0, // n <= 1
+			1: 0, // n <= 1
+			2: 1, // n > 1
+			5: 1, // n > 1
 		},
+		// Indonesian (id_ID) - always form 0
 		"id_ID": {
-			1: 0,
-			5: 0,
+			0:   0,
+			1:   0,
+			5:   0,
+			100: 0,
 		},
+		// Japanese (ja_JP) - always form 0
 		"ja_JP": {
-			1: 0,
-			2: 0,
-			5: 0,
+			0:   0,
+			1:   0,
+			2:   0,
+			5:   0,
+			100: 0,
 		},
+		// Polish (pl_PL) - 3 forms
 		"pl_PL": {
-			1: 0,
-			2: 1,
-			5: 2,
-		},
+			1:  0, // n == 1
+			2:  1, // n%10 >= 2 && n%10 <= 4 && (n%100 < 10 || n%100 >= 20)
+			3:  1, // n%10 >= 2 && n%10 <= 4 && (n%100 < 10 || n%100 >= 20)
+			4:  1, // n%10 >= 2 && n%10 <= 4 && (n%100 < 10 || n%100 >= 20)
+			5:  2, // default case
+			10: 2, // default case (n%100 < 10, but n%10 not in 2-4)
+			11: 2, // default case (n%100 >= 10 and < 20)
+			12: 2, // default case (n%100 >= 10 and < 20)
+			22: 1, // n%10 >= 2 && n%10 <= 4 && (n%100 >= 20)
+			24: 1, // n%10 >= 2 && n%10 <= 4 && (n%100 >= 20)
+		},
+		// Portuguese Brazilian (pt_BR) - uses default rule
 		"pt_BR": {
-			1: 0,
-			2: 1,
-			5: 1,
+			0: 0, // n <= 1
+			1: 0, // n <= 1
+			2: 1, // n > 1
+			5: 1, // n > 1
 		},
+		// Romanian (ro_RO) - 3 forms
 		"ro_RO": {
-			1: 0,
-			2: 1,
-			5: 1,
-		},
+			0:   1, // n == 0 || (n%100 > 0 && n%100 < 20)
+			1:   0, // n == 1
+			2:   1, // n == 0 || (n%100 > 0 && n%100 < 20)
+			5:   1, // n == 0 || (n%100 > 0 && n%100 < 20)
+			19:  1, // n == 0 || (n%100 > 0 && n%100 < 20)
+			20:  2, // default case
+			21:  2, // default case
+			100: 2, // default case (n%100 == 0, so condition fails)
+			101: 1, // n%100 == 1, so n%100 > 0 && n%100 < 20
+		},
+		// Russian (ru_RU) - 3 forms
 		"ru_RU": {
-			1: 0,
-			2: 1,
-			5: 2,
-		},
+			1:  0, // n%10 == 1 && n%100 != 11
+			2:  1, // n%10 >= 2 && n%10 <= 4 && (n%100 < 10 || n%100 >= 20)
+			3:  1, // n%10 >= 2 && n%10 <= 4 && (n%100 < 10 || n%100 >= 20)
+			4:  1, // n%10 >= 2 && n%10 <= 4 && (n%100 < 10 || n%100 >= 20)
+			5:  2, // default case
+			11: 2, // n%10 == 1 but n%100 == 11, so default case
+			12: 2, // default case
+			21: 0, // n%10 == 1 && n%100 != 11
+			22: 1, // n%10 >= 2 && n%10 <= 4 && (n%100 >= 20)
+		},
+		// Serbian (sr_RS) - same as Russian
 		"sr_RS": {
-			1: 0,
-			2: 1,
-			5: 2,
+			1:  0, // n%10 == 1 && n%100 != 11
+			2:  1, // n%10 >= 2 && n%10 <= 4 && (n%100 < 10 || n%100 >= 20)
+			5:  2, // default case
+			11: 2, // n%10 == 1 but n%100 == 11, so default case
+			21: 0, // n%10 == 1 && n%100 != 11
 		},
+		// Turkish (tr_TR) - uses default rule
 		"tr_TR": {
-			1: 0,
-			2: 1,
-			5: 1,
+			0: 0, // n <= 1
+			1: 0, // n <= 1
+			2: 1, // n > 1
+			5: 1, // n > 1
 		},
+		// Ukrainian (uk_UA) - same as Russian
 		"uk_UA": {
-			1: 0,
-			2: 1,
-			5: 2,
+			1:  0, // n%10 == 1 && n%100 != 11
+			2:  1, // n%10 >= 2 && n%10 <= 4 && (n%100 < 10 || n%100 >= 20)
+			5:  2, // default case
+			11: 2, // n%10 == 1 but n%100 == 11, so default case
+			21: 0, // n%10 == 1 && n%100 != 11
 		},
+		// Chinese Simplified (zh_CN) - always form 0
 		"zh_CN": {
-			1: 0,
-			5: 0,
+			0:   0,
+			1:   0,
+			5:   0,
+			100: 0,
 		},
+		// Chinese Traditional (zh_TW) - always form 0
 		"zh_TW": {
-			1: 0,
-			5: 0,
+			0:   0,
+			1:   0,
+			5:   0,
+			100: 0,
 		},
+		// Min Nan (nan_Latn_pehoeji) - always form 0
 		"nan_Latn_pehoeji": {
-			1: 0,
-			5: 0,
+			0:   0,
+			1:   0,
+			5:   0,
+			100: 0,
+		},
+		// Additional languages from AvailableLanguages that use default rule
+		"de_DE": {
+			0: 0, // n <= 1
+			1: 0, // n <= 1
+			2: 1, // n > 1
+		},
+		"el_EL": {
+			0: 0, // n <= 1
+			1: 0, // n <= 1
+			2: 1, // n > 1
+		},
+		"en_US": {
+			0: 0, // n <= 1
+			1: 0, // n <= 1
+			2: 1, // n > 1
+		},
+		"es_ES": {
+			0: 0, // n <= 1
+			1: 0, // n <= 1
+			2: 1, // n > 1
+		},
+		"fi_FI": {
+			0: 0, // n <= 1
+			1: 0, // n <= 1
+			2: 1, // n > 1
+		},
+		"hi_IN": {
+			0: 0, // n <= 1
+			1: 0, // n <= 1
+			2: 1, // n > 1
+		},
+		"it_IT": {
+			0: 0, // n <= 1
+			1: 0, // n <= 1
+			2: 1, // n > 1
+		},
+		"nl_NL": {
+			0: 0, // n <= 1
+			1: 0, // n <= 1
+			2: 1, // n > 1
+		},
+		// Test a language not in the switch (should use default rule)
+		"unknown_language": {
+			0: 0, // n <= 1
+			1: 0, // n <= 1
+			2: 1, // n > 1
 		},
 	}
 

internal/locale/printer.go

@@ -10,6 +10,11 @@ type Printer struct {
 	language string
 }
 
+// NewPrinter creates a new Printer instance for the given language.
+func NewPrinter(language string) *Printer {
+	return &Printer{language}
+}
+
 func (p *Printer) Print(key string) string {
 	if dict, err := getTranslationDict(p.language); err == nil {
 		if str, ok := dict[key]; ok {
@@ -65,8 +70,3 @@ func (p *Printer) Plural(key string, n int, args ...interface{}) string {
 
 	return key
 }
-
-// NewPrinter creates a new Printer.
-func NewPrinter(language string) *Printer {
-	return &Printer{language}
-}

internal/locale/printer_test.go

@@ -5,7 +5,7 @@ package locale // import "miniflux.app/v2/internal/locale"
 
 import "testing"
 
-func TestTranslateWithMissingLanguage(t *testing.T) {
+func TestPrintfWithMissingLanguage(t *testing.T) {
 	defaultCatalog = catalog{}
 	translation := NewPrinter("invalid").Printf("missing.key")
 
@@ -14,7 +14,7 @@ func TestTranslateWithMissingLanguage(t *testing.T) {
 	}
 }
 
-func TestTranslateWithMissingKey(t *testing.T) {
+func TestPrintfWithMissingKey(t *testing.T) {
 	defaultCatalog = catalog{
 		"en_US": translationDict{
 			"k": "v",
@@ -27,7 +27,7 @@ func TestTranslateWithMissingKey(t *testing.T) {
 	}
 }
 
-func TestTranslateWithExistingKey(t *testing.T) {
+func TestPrintfWithExistingKey(t *testing.T) {
 	defaultCatalog = catalog{
 		"en_US": translationDict{
 			"auth.username": "Login",
@@ -40,7 +40,7 @@ func TestTranslateWithExistingKey(t *testing.T) {
 	}
 }
 
-func TestTranslateWithExistingKeyAndPlaceholder(t *testing.T) {
+func TestPrintfWithExistingKeyAndPlaceholder(t *testing.T) {
 	defaultCatalog = catalog{
 		"en_US": translationDict{
 			"key": "Test: %s",
@@ -56,7 +56,7 @@ func TestTranslateWithExistingKeyAndPlaceholder(t *testing.T) {
 	}
 }
 
-func TestTranslateWithMissingKeyAndPlaceholder(t *testing.T) {
+func TestPrintfWithMissingKeyAndPlaceholder(t *testing.T) {
 	defaultCatalog = catalog{
 		"en_US": translationDict{
 			"auth.username": "Login",
@@ -72,7 +72,7 @@ func TestTranslateWithMissingKeyAndPlaceholder(t *testing.T) {
 	}
 }
 
-func TestTranslateWithInvalidValue(t *testing.T) {
+func TestPrintfWithInvalidValue(t *testing.T) {
 	defaultCatalog = catalog{
 		"en_US": translationDict{
 			"auth.username": "Login",
@@ -88,7 +88,134 @@ func TestTranslateWithInvalidValue(t *testing.T) {
 	}
 }
 
-func TestTranslatePluralWithDefaultRule(t *testing.T) {
+func TestPrintWithMissingLanguage(t *testing.T) {
+	defaultCatalog = catalog{}
+	translation := NewPrinter("invalid").Print("missing.key")
+
+	if translation != "missing.key" {
+		t.Errorf(`Wrong translation, got %q`, translation)
+	}
+}
+
+func TestPrintWithMissingKey(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"existing.key": "value",
+		},
+	}
+
+	translation := NewPrinter("en_US").Print("missing.key")
+	if translation != "missing.key" {
+		t.Errorf(`Wrong translation, got %q`, translation)
+	}
+}
+
+func TestPrintWithExistingKey(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"auth.username": "Login",
+		},
+	}
+
+	translation := NewPrinter("en_US").Print("auth.username")
+	if translation != "Login" {
+		t.Errorf(`Wrong translation, got %q`, translation)
+	}
+}
+
+func TestPrintWithDifferentLanguages(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"greeting": "Hello",
+		},
+		"fr_FR": translationDict{
+			"greeting": "Bonjour",
+		},
+		"es_ES": translationDict{
+			"greeting": "Hola",
+		},
+	}
+
+	tests := []struct {
+		language string
+		expected string
+	}{
+		{"en_US", "Hello"},
+		{"fr_FR", "Bonjour"},
+		{"es_ES", "Hola"},
+	}
+
+	for _, test := range tests {
+		translation := NewPrinter(test.language).Print("greeting")
+		if translation != test.expected {
+			t.Errorf(`Wrong translation for %s, got %q instead of %q`, test.language, translation, test.expected)
+		}
+	}
+}
+
+func TestPrintWithInvalidTranslationType(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"valid.key":   "valid string",
+			"invalid.key": 12345, // not a string
+		},
+	}
+
+	printer := NewPrinter("en_US")
+
+	// Valid string should work
+	translation := printer.Print("valid.key")
+	if translation != "valid string" {
+		t.Errorf(`Wrong translation for valid key, got %q`, translation)
+	}
+
+	// Invalid type should return the key itself
+	translation = printer.Print("invalid.key")
+	if translation != "invalid.key" {
+		t.Errorf(`Wrong translation for invalid key, got %q`, translation)
+	}
+}
+
+func TestPrintWithNilTranslation(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"nil.key": nil,
+		},
+	}
+
+	translation := NewPrinter("en_US").Print("nil.key")
+	if translation != "nil.key" {
+		t.Errorf(`Wrong translation for nil value, got %q`, translation)
+	}
+}
+
+func TestPrintWithEmptyKey(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"": "empty key translation",
+		},
+	}
+
+	translation := NewPrinter("en_US").Print("")
+	if translation != "empty key translation" {
+		t.Errorf(`Wrong translation for empty key, got %q`, translation)
+	}
+}
+
+func TestPrintWithEmptyTranslation(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"empty.value": "",
+		},
+	}
+
+	translation := NewPrinter("en_US").Print("empty.value")
+	if translation != "" {
+		t.Errorf(`Wrong translation for empty value, got %q`, translation)
+	}
+}
+
+func TestPluralWithDefaultRule(t *testing.T) {
 	defaultCatalog = catalog{
 		"en_US": translationDict{
 			"number_of_users": []string{"%d user (%s)", "%d users (%s)"},
@@ -112,7 +239,7 @@ func TestTranslatePluralWithDefaultRule(t *testing.T) {
 	}
 }
 
-func TestTranslatePluralWithRussianRule(t *testing.T) {
+func TestPluralWithRussianRule(t *testing.T) {
 	defaultCatalog = catalog{
 		"en_US": translationDict{
 			"time_elapsed.years": []string{"%d year", "%d years"},
@@ -143,7 +270,7 @@ func TestTranslatePluralWithRussianRule(t *testing.T) {
 	}
 }
 
-func TestTranslatePluralWithMissingTranslation(t *testing.T) {
+func TestPluralWithMissingTranslation(t *testing.T) {
 	defaultCatalog = catalog{
 		"en_US": translationDict{
 			"number_of_users": []string{"%d user (%s)", "%d users (%s)"},
@@ -157,7 +284,7 @@ func TestTranslatePluralWithMissingTranslation(t *testing.T) {
 	}
 }
 
-func TestTranslatePluralWithInvalidValues(t *testing.T) {
+func TestPluralWithInvalidValues(t *testing.T) {
 	defaultCatalog = catalog{
 		"en_US": translationDict{
 			"number_of_users": []string{"%d user (%s)", "%d users (%s)"},
@@ -172,3 +299,126 @@ func TestTranslatePluralWithInvalidValues(t *testing.T) {
 		t.Errorf(`Wrong translation, got %q instead of %q`, translation, expected)
 	}
 }
+
+func TestPluralWithMissingLanguage(t *testing.T) {
+	defaultCatalog = catalog{}
+	translation := NewPrinter("invalid_language").Plural("test.key", 2)
+	expected := "test.key"
+	if translation != expected {
+		t.Errorf(`Wrong translation, got %q instead of %q`, translation, expected)
+	}
+}
+
+func TestPluralWithAnySliceType(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"test.key": []any{"%d item", "%d items"},
+		},
+	}
+
+	printer := NewPrinter("en_US")
+
+	translation := printer.Plural("test.key", 1, 1)
+	expected := "1 item"
+	if translation != expected {
+		t.Errorf(`Wrong translation for singular, got %q instead of %q`, translation, expected)
+	}
+
+	translation = printer.Plural("test.key", 2, 2)
+	expected = "2 items"
+	if translation != expected {
+		t.Errorf(`Wrong translation for plural, got %q instead of %q`, translation, expected)
+	}
+}
+
+func TestPluralWithMixedAnySliceTypes(t *testing.T) {
+	defaultCatalog = catalog{
+		"en_US": translationDict{
+			"mixed.key": []any{"single: %s", "multiple: %s", "many: %s"},
+		},
+	}
+
+	printer := NewPrinter("en_US")
+
+	// Test first element (should convert first any element to string)
+	translation := printer.Plural("mixed.key", 0, "test") // n=0 uses index 0
+	expected := "single: test"
+	if translation != expected {
+		t.Errorf(`Wrong translation for index 0, got %q instead of %q`, translation, expected)
+	}
+
+	// Test second element (should use plural form)
+	translation = printer.Plural("mixed.key", 2, "items") // plural form for default language
+	expected = "multiple: items"
+	if translation != expected {
+		t.Errorf(`Wrong translation for index 1, got %q instead of %q`, translation, expected)
+	}
+}
+
+func TestPluralWithIndexOutOfBounds(t *testing.T) {
+	defaultCatalog = catalog{
+		"test_lang": translationDict{
+			"limited.key": []string{"only one form"},
+		},
+	}
+
+	// Force a scenario where getPluralForm might return an index >= len(plurals)
+	// We'll create a scenario with Czech language rules
+	defaultCatalog["cs_CZ"] = translationDict{
+		"limited.key": []string{"one form only"}, // Only one form, but Czech has 3 plural forms
+	}
+
+	printer := NewPrinter("cs_CZ")
+	// n=5 should return index 2 for Czech, but we only have 1 form (index 0)
+	translation := printer.Plural("limited.key", 5)
+	expected := "limited.key"
+	if translation != expected {
+		t.Errorf(`Wrong translation for out of bounds index, got %q instead of %q`, translation, expected)
+	}
+}
+
+func TestPluralWithVariousLanguageRules(t *testing.T) {
+	defaultCatalog = catalog{
+		"ar_AR": translationDict{
+			"items": []string{"no items", "one item", "two items", "few items", "many items", "other items"},
+		},
+		"pl_PL": translationDict{
+			"files": []string{"one file", "few files", "many files"},
+		},
+		"ja_JP": translationDict{
+			"photos": []string{"photos"},
+		},
+	}
+
+	tests := []struct {
+		language string
+		key      string
+		n        int
+		expected string
+	}{
+		// Arabic tests
+		{"ar_AR", "items", 0, "no items"},
+		{"ar_AR", "items", 1, "one item"},
+		{"ar_AR", "items", 2, "two items"},
+		{"ar_AR", "items", 5, "few items"},   // n%100 >= 3 && n%100 <= 10
+		{"ar_AR", "items", 15, "many items"}, // n%100 >= 11
+
+		// Polish tests
+		{"pl_PL", "files", 1, "one file"},
+		{"pl_PL", "files", 3, "few files"},  // n%10 >= 2 && n%10 <= 4
+		{"pl_PL", "files", 5, "many files"}, // default case
+
+		// Japanese tests (always uses same form)
+		{"ja_JP", "photos", 1, "photos"},
+		{"ja_JP", "photos", 10, "photos"},
+	}
+
+	for _, test := range tests {
+		printer := NewPrinter(test.language)
+		translation := printer.Plural(test.key, test.n)
+		if translation != test.expected {
+			t.Errorf(`Wrong translation for %s with n=%d, got %q instead of %q`,
+				test.language, test.n, translation, test.expected)
+		}
+	}
+}