test(12-07): add PlanRepository getNextNumber tests

Add tests for getNextNumber method:
- Returns 1 for phase with no plans
- Returns max + 1 for phase with existing plans
- Not affected by plans in other phases

src/db/repositories/drizzle/plan.test.ts

@@ -118,6 +118,41 @@ describe('DrizzlePlanRepository', () => {
     });
   });
 
+  describe('getNextNumber', () => {
+    it('should return 1 for phase with no plans', async () => {
+      const nextNumber = await planRepo.getNextNumber(testPhaseId);
+      expect(nextNumber).toBe(1);
+    });
+
+    it('should return max + 1 for phase with plans', async () => {
+      await planRepo.create({ phaseId: testPhaseId, number: 1, name: 'Plan 1' });
+      await planRepo.create({ phaseId: testPhaseId, number: 5, name: 'Plan 5' });
+
+      const nextNumber = await planRepo.getNextNumber(testPhaseId);
+      expect(nextNumber).toBe(6);
+    });
+
+    it('should not be affected by plans in other phases', async () => {
+      // Create another phase
+      const initiative = await initiativeRepo.create({ name: 'Another Initiative' });
+      const otherPhase = await phaseRepo.create({
+        initiativeId: initiative.id,
+        number: 2,
+        name: 'Other Phase',
+      });
+
+      // Add plans to other phase
+      await planRepo.create({ phaseId: otherPhase.id, number: 10, name: 'High Plan' });
+
+      // Add a plan to test phase
+      await planRepo.create({ phaseId: testPhaseId, number: 3, name: 'Plan 3' });
+
+      // Next number for test phase should be 4, not 11
+      const nextNumber = await planRepo.getNextNumber(testPhaseId);
+      expect(nextNumber).toBe(4);
+    });
+  });
+
   describe('update', () => {
     it('should update fields and updatedAt', async () => {
       const created = await planRepo.create({