Add Task model validation test and clean up (#44)

## Summary
- remove old test file
- ensure Jest uses `test` directory
- add unit test verifying Task schema rejects past due dates

## Testing
- `npm test`

------
https://chatgpt.com/codex/tasks/task_e_6847db999720832a84b1770922e0db84

Author: temichelle13

jest.config.js

@@ -1,17 +1,17 @@
-module.exports = {
-    testEnvironment: 'node',
-    verbose: true,
-    collectCoverage: true,
-    coverageDirectory: 'coverage',
-    testPathIgnorePatterns: ['/node_modules/'],
-    coveragePathIgnorePatterns: ['/node_modules/', '/tests/'],
-    coverageThreshold: {
-      global: {
-        branches: 70,
-        functions: 80,
-        lines: 80,
-        statements: 80
-      }
-    }
-  };
-  
+module.exports = {
+    testEnvironment: 'node',
+    verbose: true,
+    collectCoverage: true,
+    coverageDirectory: 'coverage',
+    testPathIgnorePatterns: ['/node_modules/'],
+    coveragePathIgnorePatterns: ['/node_modules/', '/tests/'],
+    roots: ['<rootDir>', '<rootDir>/test'],
+    coverageThreshold: {
+      global: {
+        branches: 70,
+        functions: 80,
+        lines: 80,
+        statements: 80
+      }
+    }
+};

test/taskModel.test.js

@@ -0,0 +1,18 @@
+const mongoose = require('mongoose');
+const Task = require('../models/task');
+
+describe('Task Model Validation', () => {
+  it('should fail validation for past dueDate', async () => {
+    const pastDate = new Date(Date.now() - 24 * 60 * 60 * 1000); // yesterday
+    const task = new Task({ title: 'Past Due Task', dueDate: pastDate });
+
+    try {
+      await task.validate();
+      // If validate does not throw, force fail
+      throw new Error('Validation should have failed for past dueDate');
+    } catch (err) {
+      expect(err).toBeInstanceOf(mongoose.Error.ValidationError);
+      expect(err.errors.dueDate).toBeDefined();
+    }
+  });
+});