diff --git a/backend/tests/test_jira_service.py b/backend/tests/test_jira_service.py
new file mode 100644
index 0000000..e683438
--- /dev/null
+++ b/backend/tests/test_jira_service.py
@@ -0,0 +1,64 @@
+"""Jira service unit tests (FASE-1.2)."""
+
+from datetime import datetime
+from unittest.mock import MagicMock, patch
+from uuid import uuid4
+
+import pytest
+
+from app.domain.exceptions import InvalidOperationError
+from app.models.jira_link import JiraLink, JiraLinkEntityType
+from app.services import jira_service
+
+
+def test_get_jira_client_raises_when_disabled(monkeypatch):
+    monkeypatch.setattr("app.services.jira_service.settings.JIRA_ENABLED", False)
+    jira_service._jira_client = None
+    with pytest.raises(InvalidOperationError, match="not enabled"):
+        jira_service.get_jira_client()
+
+
+@patch("app.services.jira_service.get_jira_client")
+def test_sync_aegis_to_jira_adds_comment(mock_get_client, db):
+    mock_jira = MagicMock()
+    mock_get_client.return_value = mock_jira
+
+    link = JiraLink(
+        entity_type=JiraLinkEntityType.test,
+        entity_id=uuid4(),
+        jira_issue_key="SEC-99",
+    )
+    jira_service.sync_aegis_to_jira(db, link, {"state": "validated", "result": "pass"})
+
+    mock_jira.issue_add_comment.assert_called_once()
+    args = mock_jira.issue_add_comment.call_args[0]
+    assert args[0] == "SEC-99"
+    assert "Aegis Sync Update" in args[1]
+    assert link.last_synced_at is not None
+
+
+@patch("app.services.jira_service.get_jira_client")
+def test_search_jira_issues_maps_fields(mock_get_client):
+    mock_jira = MagicMock()
+    mock_get_client.return_value = mock_jira
+    mock_jira.jql.return_value = {
+        "issues": [
+            {
+                "key": "TST-1",
+                "fields": {
+                    "summary": "Test issue",
+                    "status": {"name": "In Progress"},
+                    "assignee": {"displayName": "Alice"},
+                    "priority": {"name": "High"},
+                },
+            }
+        ]
+    }
+
+    results = jira_service.search_jira_issues("project = TEST", max_results=5)
+
+    assert len(results) == 1
+    assert results[0]["issue_key"] == "TST-1"
+    assert results[0]["summary"] == "Test issue"
+    assert results[0]["status"] == "In Progress"
+    mock_jira.jql.assert_called_once()