src/hooks/useBudget.test.ts

@@ -359,6 +359,11 @@ describe("buildBudgetYearRows — a category whose parent is deleted or gone (#3
     );
     expect(rows.some((r) => r.category_id === 7 || r.category_id === 8)).toBe(false);
   });
+
+  it("hides a category that is its own parent too, a loop of one member", () => {
+    const rows = buildBudgetYearRows([...CATEGORIES, cat(7, "Gifts", "expense", { parent_id: 7 })], [entry(7, 40)], []);
+    expect(rows.some((r) => r.category_id === 7)).toBe(false);
+  });
 });
 
 describe("buildBudgetYearRows + multi-level collapse (issue #289 end-to-end)", () => {

src/pages/CategoriesPage.render.test.tsx

@@ -202,6 +202,35 @@ describe("CategoriesPage — « Vérifier la hiérarchie » (#393)", () => {
     expect(render()).toContain("t(categories.hierarchy.errors.too_deep)");
   });
 
+  it("hands the window every category, not the tree: an orphan in a loop is named", () => {
+    const node = (id: number, name: string, parent_id: number | null) => ({
+      id,
+      name,
+      parent_id,
+      color: null,
+      icon: null,
+      type: "expense",
+      is_active: true,
+      is_inputable: true,
+      sort_order: id,
+      keyword_count: 0,
+      i18n_key: null,
+      children: [],
+    });
+    // 3 <-> 5: no root reaches them, so the tree holds root 1 (and 10 under it) only.
+    const categories = [node(1, "Logement", null), node(10, "Loyer", 1), node(3, "Cadeaux", 5), node(5, "Fêtes", 3)];
+    harness.state = {
+      isLoading: false,
+      categories,
+      tree: [{ ...categories[0], children: [categories[1]] }],
+      hierarchyCheck: { orphans: [{ id: 3, reason: "cycle" }], error: null },
+    };
+    const html = render();
+    expect(html).toContain(">Cadeaux</p>");
+    expect(html).toContain('aria-label="t(categories.hierarchy.newParentFor[name=Cadeaux])"');
+    expect(html).not.toContain(">—</p>");
+  });
+
   it("translates a refused save of the form by its key, and shows any other failure as is", () => {
     harness.state = { error: { key: "categories.hierarchy.errors.parent_has_transactions" } };
     expect(render()).toContain(">t(categories.hierarchy.errors.parent_has_transactions)</div>");

src/utils/categoryHierarchy.test.ts

@@ -113,6 +113,10 @@ describe("displaysAsRoot", () => {
     expect(displaysAsRoot({ id: 10, parent_id: 1 }, ids)).toBe(false);
     expect(displaysAsRoot({ id: 1, parent_id: 2 }, ids)).toBe(false);
   });
+
+  it("is not a root as its own parent: that one-member loop stays hidden, like the tree hides it", () => {
+    expect(displaysAsRoot({ id: 10, parent_id: 10 }, ids)).toBe(false);
+  });
 });
 
 describe("isActiveRow", () => {
@@ -139,6 +143,11 @@ describe("findOrphans (#393)", () => {
     expect(findOrphans(rows)).toEqual([{ id: 3, reason: "cycle" }]);
   });
 
+  it("names the loop by its own smallest member, never by a smaller id that hangs under it", () => {
+    // 5 <-> 8, 2 under 5: reattaching 2 would leave 5 and 8 hidden.
+    expect(findOrphans([r(2, 5), r(5, 8), r(8, 5), r(1, null)])).toEqual([{ id: 5, reason: "cycle" }]);
+  });
+
   it("lists a three-member cycle once, by its smallest id, whatever the order of the rows", () => {
     // 6 -> 4 -> 9 -> 6, 12 under 9.
     const rows = [r(6, 4), r(4, 9), r(9, 6), r(12, 9), r(1, null)];