Add unit tests for api/validators language code validation

CHANGELOG.md

@@ -58,6 +58,7 @@ Emojis for the following are chosen based on [gitmoji](https://gitmoji.dev/).
 
 - Basic health and CORS test scaffolding was added for the API ([#29](https://github.com/scribe-org/Scribe-Server/pull/29)).
 - The CI workflow was updated to select the Go version via `go-version-file` ([#8](https://github.com/scribe-org/Scribe-Server/issues/8)) and later improved further ([#30](https://github.com/scribe-org/Scribe-Server/issues/30)).
+- Unit tests were added for the language validator functions ([#78](https://github.com/scribe-org/Scribe-Server/issues/78)).
 
 ### ♻️ Code Refactoring
 

api/validators/language_validator_test.go

@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package validators
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// setSupportedLanguages configures the package-level language map for a test + restores an empty map so tests stay independent
+func setSupportedLanguages(t *testing.T, langs []string) {
+	t.Helper()
+
+	InitLanguageValidator(langs)
+	t.Cleanup(func() { InitLanguageValidator(nil) })
+}
+
+func TestInitLanguageValidator(t *testing.T) {
+	t.Cleanup(func() { InitLanguageValidator(nil) })
+
+	t.Run("supports the given languages", func(t *testing.T) {
+		InitLanguageValidator([]string{"en", "de"})
+
+		assert.True(t, IsValidLanguageCode("en"))
+		assert.True(t, IsValidLanguageCode("de"))
+		assert.False(t, IsValidLanguageCode("fr"))
+	})
+
+	t.Run("replaces previous languages", func(t *testing.T) {
+		InitLanguageValidator([]string{"en", "de"})
+		InitLanguageValidator([]string{"fr"})
+
+		assert.True(t, IsValidLanguageCode("fr"))
+		assert.False(t, IsValidLanguageCode("en"))
+		assert.False(t, IsValidLanguageCode("de"))
+	})
+
+	t.Run("nil list clears all languages", func(t *testing.T) {
+		InitLanguageValidator([]string{"en"})
+		InitLanguageValidator(nil)
+
+		assert.False(t, IsValidLanguageCode("en"))
+	})
+
+	t.Run("empty list clears all languages", func(t *testing.T) {
+		InitLanguageValidator([]string{"en"})
+		InitLanguageValidator([]string{})
+
+		assert.False(t, IsValidLanguageCode("en"))
+	})
+
+	t.Run("duplicate entries are accepted", func(t *testing.T) {
+		InitLanguageValidator([]string{"en", "en"})
+
+		assert.True(t, IsValidLanguageCode("en"))
+	})
+}
+
+func TestIsValidLanguageCode(t *testing.T) {
+	setSupportedLanguages(t, []string{"en", "de", "fr"})
+
+	tests := []struct {
+		name string
+		code string
+		want bool
+	}{
+		{name: "supported code", code: "en", want: true},
+		{name: "another supported code", code: "de", want: true},
+		{name: "valid format but unsupported", code: "es", want: false},
+		{name: "uppercase code", code: "EN", want: false},
+		{name: "mixed case code", code: "En", want: false},
+		{name: "empty code", code: "", want: false},
+		{name: "single character", code: "e", want: false},
+		{name: "three characters", code: "eng", want: false},
+		{name: "leading whitespace", code: " e", want: false},
+		{name: "trailing whitespace", code: "en ", want: false},
+		{name: "digits", code: "12", want: false},
+		{name: "SQL injection attempt", code: "en; DROP TABLE", want: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.want, IsValidLanguageCode(tt.code))
+		})
+	}
+}
+
+func TestIsValidLanguageCode_NoLanguagesConfigured(t *testing.T) {
+	setSupportedLanguages(t, nil)
+
+	assert.False(t, IsValidLanguageCode("en"))
+}
+
+func TestSanitizeLanguageCode(t *testing.T) {
+	setSupportedLanguages(t, []string{"en", "de"})
+
+	tests := []struct {
+		name string
+		code string
+		want string
+	}{
+		{name: "supported code is uppercased", code: "en", want: "EN"},
+		{name: "another supported code", code: "de", want: "DE"},
+		{name: "unsupported code", code: "fr", want: ""},
+		{name: "uppercase input is rejected", code: "EN", want: ""},
+		{name: "empty code", code: "", want: ""},
+		{name: "too long", code: "eng", want: ""},
+		{name: "injection attempt", code: "en; DROP TABLE", want: ""},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.want, SanitizeLanguageCode(tt.code))
+		})
+	}
+}
+
+func TestIsLanguageSupported(t *testing.T) {
+	tests := []struct {
+		name      string
+		lang      string
+		available []string
+		want      bool
+	}{
+		{name: "language in list", lang: "en", available: []string{"en", "de"}, want: true},
+		{name: "language not in list", lang: "fr", available: []string{"en", "de"}, want: false},
+		{name: "case sensitive", lang: "EN", available: []string{"en", "de"}, want: false},
+		{name: "empty list", lang: "en", available: []string{}, want: false},
+		{name: "nil list", lang: "en", available: nil, want: false},
+		{name: "empty language not in list", lang: "", available: []string{"en"}, want: false},
+		{name: "empty language in list", lang: "", available: []string{""}, want: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.want, IsLanguageSupported(tt.lang, tt.available))
+		})
+	}
+}
+
+func TestIsValidTranslationLangCode(t *testing.T) {
+	tests := []struct {
+		name string
+		code string
+		want bool
+	}{
+		{name: "two-letter code", code: "de", want: true},
+		{name: "three-letter code", code: "pnb", want: true},
+		{name: "four-letter code", code: "abcd", want: true},
+		{name: "uppercase code", code: "DE", want: false},
+		{name: "mixed case code", code: "dE", want: false},
+		{name: "empty code", code: "", want: false},
+		{name: "single letter", code: "d", want: false},
+		{name: "five letters", code: "abcde", want: false},
+		{name: "digits", code: "d1", want: false},
+		{name: "hyphen", code: "de-", want: false},
+		{name: "leading whitespace", code: " de", want: false},
+		{name: "trailing newline", code: "de\n", want: false},
+		{name: "non-ASCII letters", code: "dé", want: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.want, IsValidTranslationLangCode(tt.code))
+		})
+	}
+}