test: add comprehensive tests for findLanguageCodesForDuplicateLabels

- Added test coverage for undefined value handling
- Tests verify fix for TypeError when language keys are missing
- Added test script to types package.json
- All 7 tests passing

packages/types/package.json

@@ -6,7 +6,9 @@
   "sideEffects": false,
   "scripts": {
     "lint": "eslint . --ext .ts,.js,.tsx,.jsx",
-    "clean": "rimraf node_modules .turbo"
+    "clean": "rimraf node_modules .turbo",
+    "test": "vitest run",
+    "test:coverage": "vitest run --coverage"
   },
   "dependencies": {
     "@prisma/client": "6.14.0",
@@ -16,6 +18,7 @@
   },
   "devDependencies": {
     "@formbricks/config-typescript": "workspace:*",
-    "@formbricks/database": "workspace:*"
+    "@formbricks/database": "workspace:*",
+    "vitest": "3.0.1"
   }
 }

packages/types/surveys/validation.test.ts

@@ -0,0 +1,108 @@
+import { describe, expect, it } from "vitest";
+import type { TI18nString } from "../i18n";
+import type { TSurveyLanguage } from "./types";
+import { findLanguageCodesForDuplicateLabels } from "./validation";
+
+describe("findLanguageCodesForDuplicateLabels", () => {
+  const mockLanguages: TSurveyLanguage[] = [
+    {
+      default: true,
+      enabled: true,
+      language: { id: "en", code: "en", alias: null, createdAt: new Date(), updatedAt: new Date() },
+    },
+    {
+      default: false,
+      enabled: true,
+      language: { id: "es", code: "es", alias: null, createdAt: new Date(), updatedAt: new Date() },
+    },
+  ];
+
+  it("should handle undefined language values without throwing", () => {
+    const labels: TI18nString[] = [
+      { default: "Option 1", es: "Opción 1" },
+      { default: "Option 2" }, // Missing 'es' key - this was causing the error
+      { default: "Option 3", es: "Opción 3" },
+    ];
+
+    // This should not throw a TypeError
+    expect(() => findLanguageCodesForDuplicateLabels(labels, mockLanguages)).not.toThrow();
+  });
+
+  it("should detect duplicates when labels are the same", () => {
+    const labels: TI18nString[] = [
+      { default: "Option 1", es: "Opción 1" },
+      { default: "Option 1", es: "Opción 1" }, // Duplicate
+      { default: "Option 3", es: "Opción 3" },
+    ];
+
+    const result = findLanguageCodesForDuplicateLabels(labels, mockLanguages);
+    expect(result).toContain("default");
+    expect(result).toContain("es");
+  });
+
+  it("should not detect duplicates when labels are different", () => {
+    const labels: TI18nString[] = [
+      { default: "Option 1", es: "Opción 1" },
+      { default: "Option 2", es: "Opción 2" },
+      { default: "Option 3", es: "Opción 3" },
+    ];
+
+    const result = findLanguageCodesForDuplicateLabels(labels, mockLanguages);
+    expect(result).toHaveLength(0);
+  });
+
+  it("should ignore empty strings when detecting duplicates", () => {
+    const labels: TI18nString[] = [
+      { default: "Option 1", es: "Opción 1" },
+      { default: "", es: "" }, // Empty strings
+      { default: "  ", es: "  " }, // Whitespace-only strings
+      { default: "Option 2", es: "Opción 2" },
+    ];
+
+    const result = findLanguageCodesForDuplicateLabels(labels, mockLanguages);
+    expect(result).toHaveLength(0);
+  });
+
+  it("should handle mixed scenarios with undefined and duplicates", () => {
+    const labels: TI18nString[] = [
+      { default: "Option 1" }, // Missing 'es'
+      { default: "Option 2", es: "Opción" },
+      { default: "Option 2", es: "Opción" }, // Duplicate in both languages
+    ];
+
+    const result = findLanguageCodesForDuplicateLabels(labels, mockLanguages);
+    expect(result).toContain("default");
+    expect(result).toContain("es");
+  });
+
+  it("should work with only default language enabled", () => {
+    const defaultOnlyLanguages: TSurveyLanguage[] = [
+      {
+        default: true,
+        enabled: true,
+        language: { id: "en", code: "en", alias: null, createdAt: new Date(), updatedAt: new Date() },
+      },
+    ];
+
+    const labels: TI18nString[] = [
+      { default: "Option 1" },
+      { default: "Option 1" }, // Duplicate
+    ];
+
+    const result = findLanguageCodesForDuplicateLabels(labels, defaultOnlyLanguages);
+    expect(result).toContain("default");
+  });
+
+  it("should handle completely undefined values gracefully", () => {
+    const labels: TI18nString[] = [
+      { default: "Option 1" },
+      { default: "Option 2" },
+      {} as TI18nString, // Empty object - all languages undefined
+    ];
+
+    // This should not throw
+    expect(() => findLanguageCodesForDuplicateLabels(labels, mockLanguages)).not.toThrow();
+    const result = findLanguageCodesForDuplicateLabels(labels, mockLanguages);
+    expect(result).toHaveLength(0);
+  });
+});