fix: teacher entity had geen constructor

backend/tests/data/teachers.test.ts

@@ -0,0 +1,51 @@
+import { setupTestApp } from '../setup-tests.js';
+import { describe, it, expect, beforeAll } from 'vitest';
+import { TeacherRepository } from '../../src/data/users/teacher-repository.js';
+import { Teacher } from '../../src/entities/users/teacher.entity.js';
+import { getTeacherRepository } from '../../src/data/repositories.js';
+
+const username = 'testteacher';
+const firstName = 'John';
+const lastName = 'Doe';
+describe('TeacherRepository', () => {
+    let TeacherRepository: TeacherRepository;
+
+    beforeAll(async () => {
+        await setupTestApp();
+        TeacherRepository = getTeacherRepository();
+    });
+
+    it('should not return a teacher because username does not exist', async() => {
+        const student = await TeacherRepository.findByUsername('test');
+
+        expect(student).toBeNull();
+    });
+
+    it('should return teacher from the datbase', async() => {
+        const student = await TeacherRepository.findByUsername('Tool');
+
+        expect(student).toBeTruthy();
+        expect(student?.firstName).toBe('Maynard');
+        expect(student?.lastName).toBe('Keenan');
+    })
+
+    it('should return the queried teacher after he was added', async () => {
+        await TeacherRepository.insert(
+            new Teacher(username, firstName, lastName)
+        );
+
+        const retrievedStudent =
+            await TeacherRepository.findByUsername(username);
+        expect(retrievedStudent).toBeTruthy();
+        expect(retrievedStudent?.firstName).toBe(firstName);
+        expect(retrievedStudent?.lastName).toBe(lastName);
+    });
+
+    it('should no longer return the queried student after he was removed again', async () => {
+        await TeacherRepository.deleteByUsername(username);
+
+        const retrievedStudent =
+            await TeacherRepository.findByUsername(username);
+        expect(retrievedStudent).toBeNull();
+    });
+});