diff --git a/packages/api/src/__tests__/assistant-tools-timeline-allocation-mutation-test-helpers.ts b/packages/api/src/__tests__/assistant-tools-timeline-allocation-mutation-test-helpers.ts
new file mode 100644
index 0000000..106ad31
--- /dev/null
+++ b/packages/api/src/__tests__/assistant-tools-timeline-allocation-mutation-test-helpers.ts
@@ -0,0 +1,55 @@
+export const baseAvailability = {
+  monday: 8,
+  tuesday: 8,
+  wednesday: 8,
+  thursday: 8,
+  friday: 8,
+  saturday: 0,
+  sunday: 0,
+};
+
+export function buildBaseProject() {
+  return {
+    id: "project_1",
+    name: "Gelddruckmaschine",
+    shortCode: "GDM",
+    status: "ACTIVE",
+    responsiblePerson: null,
+  };
+}
+
+export function buildBaseResource(id = "resource_1") {
+  return {
+    id,
+    eid: id === "resource_1" ? "E-001" : `E-${id}`,
+    displayName: id === "resource_1" ? "Alice" : `Resource ${id}`,
+    lcrCents: 5000,
+    availability: {
+      ...baseAvailability,
+    },
+  };
+}
+
+export function buildBaseAssignment() {
+  return {
+    id: "assignment_1",
+    demandRequirementId: null,
+    resourceId: "resource_1",
+    projectId: "project_1",
+    startDate: new Date("2026-03-16"),
+    endDate: new Date("2026-03-20"),
+    hoursPerDay: 4,
+    percentage: 50,
+    role: "Compositor",
+    roleId: "role_comp",
+    dailyCostCents: 20000,
+    status: "PROPOSED",
+    metadata: {},
+    createdAt: new Date("2026-03-13"),
+    updatedAt: new Date("2026-03-13"),
+    resource: buildBaseResource(),
+    project: { id: "project_1", name: "Project One", shortCode: "PRJ" },
+    roleEntity: { id: "role_comp", name: "Compositor", color: "#111111" },
+    demandRequirement: null,
+  };
+}