test: improve testing coverage for prompt package

- Add a new test file for the `prompt` package
- Implement a test for the `GetLanguage` function

Signed-off-by: Bo-Yi.Wu <appleboy.tw@gmail.com>

Author: appleboy

prompt/language_test.go

@@ -0,0 +1,23 @@
+package prompt
+
+import "testing"
+
+func TestGetLanguage(t *testing.T) {
+	testCases := []struct {
+		langCode string
+		expected string
+	}{
+		{"en", DefaultLanguage},
+		{"zh-tw", "Traditional Chinese"},
+		{"zh-cn", "Simplified Chinese"},
+		{"ja", "Japanese"},
+		{"fr", DefaultLanguage},
+	}
+
+	for _, tc := range testCases {
+		result := GetLanguage(tc.langCode)
+		if result != tc.expected {
+			t.Errorf("GetLanguage(%q) = %q, expected %q", tc.langCode, result, tc.expected)
+		}
+	}
+}