diff --git a/backend/tests/test_campaign_approval.py b/backend/tests/test_campaign_approval.py
index c920fe0..536a755 100644
--- a/backend/tests/test_campaign_approval.py
+++ b/backend/tests/test_campaign_approval.py
@@ -1,5 +1,7 @@
 """Tests for the campaign manager-approval workflow."""
 
+import uuid
+
 import pytest
 
 from app.models.campaign import Campaign, CampaignTest
@@ -70,6 +72,12 @@ class TestSubmitCampaignForApproval:
                 submitter_id=admin_user.id, submitter_role="admin",
             )
 
+    def test_submit_nonexistent_campaign_raises(self, db, admin_user):
+        with pytest.raises(EntityNotFoundError):
+            submit_campaign_for_approval(
+                db, str(uuid.uuid4()), submitter_id=admin_user.id, submitter_role="admin",
+            )
+
 
 class TestApproveCampaign:
     def test_approve_sets_start_date_and_activates(self, db, draft_campaign_with_test, admin_user):
@@ -101,6 +109,12 @@ class TestApproveCampaign:
                 approver_id=admin_user.id, start_date="2026-08-01T00:00:00",
             )
 
+    def test_approve_nonexistent_campaign_raises(self, db, admin_user):
+        with pytest.raises(EntityNotFoundError):
+            approve_campaign(
+                db, str(uuid.uuid4()), approver_id=admin_user.id, start_date="2026-08-01T00:00:00",
+            )
+
 
 class TestRejectCampaign:
     def test_reject_returns_to_draft_with_reason(self, db, draft_campaign_with_test, admin_user):
@@ -126,3 +140,31 @@ class TestRejectCampaign:
     def test_reject_non_pending_raises(self, db, draft_campaign_with_test, admin_user):
         with pytest.raises(BusinessRuleViolation, match="pending approval"):
             reject_campaign(db, str(draft_campaign_with_test.id), rejecter_id=admin_user.id, reason="No")
+
+    def test_reject_clears_prior_approval_fields(self, db, draft_campaign_with_test, admin_user):
+        submit_campaign_for_approval(
+            db, str(draft_campaign_with_test.id), submitter_id=admin_user.id, submitter_role="admin",
+        )
+        db.commit()
+        approve_campaign(
+            db, str(draft_campaign_with_test.id),
+            approver_id=admin_user.id, start_date="2026-08-01T00:00:00",
+        )
+        db.commit()
+        # Simulate the campaign being sent back into the approval queue
+        # (e.g. after a modification request) so reject_campaign has
+        # approved_by/approved_at to clear.
+        draft_campaign_with_test.status = "pending_approval"
+        db.commit()
+
+        campaign = reject_campaign(
+            db, str(draft_campaign_with_test.id),
+            rejecter_id=admin_user.id, reason="Needs rework",
+        )
+        assert campaign.status == "draft"
+        assert campaign.approved_by is None
+        assert campaign.approved_at is None
+
+    def test_reject_nonexistent_campaign_raises(self, db, admin_user):
+        with pytest.raises(EntityNotFoundError):
+            reject_campaign(db, str(uuid.uuid4()), rejecter_id=admin_user.id, reason="No")