test: add unit tests for json to csv converter

src/pages/tools/json/json-to-csv/service.test.ts

@@ -0,0 +1,61 @@
+import { describe, it, expect } from 'vitest';
+import { convertJsonToCsv } from './service';
+
+const defaultOptions: Parameters<typeof convertJsonToCsv>[1] = {
+  delimiter: ',',
+  includeHeaders: true,
+  quoteStrings: 'auto'
+};
+
+describe('convertJsonToCsv', () => {
+  it('converts simple JSON array to CSV', () => {
+    const input = JSON.stringify([
+      { name: 'Dhee', age: 20 },
+      { name: 'Jarvis', age: 999 }
+    ]);
+
+    const result = convertJsonToCsv(input, defaultOptions);
+
+    expect(result).toBe(
+      `name,age
+Dhee,20
+Jarvis,999`
+    );
+  });
+
+  it('handles a single object', () => {
+    const input = JSON.stringify({
+      name: 'Dhee',
+      age: 20
+    });
+
+    const result = convertJsonToCsv(input, defaultOptions);
+
+    expect(result).toBe(
+      `name,age
+Dhee,20`
+    );
+  });
+
+  it('flattens nested objects', () => {
+    const input = JSON.stringify([
+      {
+        name: 'Dhee',
+        info: { age: 20, city: 'Pune' }
+      }
+    ]);
+
+    const result = convertJsonToCsv(input, defaultOptions);
+
+    expect(result).toBe(
+      `name,info.age,info.city
+Dhee,20,Pune`
+    );
+  });
+
+  it('throws error for invalid JSON', () => {
+    const input = 'invalid json';
+
+    expect(() => convertJsonToCsv(input, defaultOptions)).toThrow();
+  });
+});