test: PopulationSelector コンポーネントのテスト追加

src/tests/PopulationSelector.test.tsx

@@ -0,0 +1,51 @@
+import React from "react";
+import { render, screen, fireEvent, waitFor } from "@testing-library/react";
+import PopulationSelector from "./../components/PopulationSelector";
+import { fetchPopulation } from "../api/population";
+import { Prefecture } from "../types/prefecture";
+import { PopulationCategory } from "../types/population";
+
+jest.mock("../api/population");
+
+describe("PopulationSelector", () => {
+  const mockPrefectures: Prefecture[] = [
+    { prefCode: 1, prefName: "北海道" },
+    { prefCode: 2, prefName: "青森県" },
+  ];
+
+  it("都道府県を選択し、人口データが表示される", async () => {
+    const mockPopulationData: PopulationCategory[] = [
+      {
+        label: "年少人口",
+        data: [{ year: 1960, value: 1681479, rate: 33.37 }],
+      },
+    ];
+
+    (fetchPopulation as jest.Mock).mockResolvedValue(mockPopulationData);
+
+    render(<PopulationSelector prefectures={mockPrefectures} />);
+
+    fireEvent.change(screen.getByRole("combobox"), { target: { value: "1" } });
+
+    await waitFor(() => screen.getByText("年少人口"));
+
+    expect(screen.getByText("年少人口")).toBeInTheDocument();
+    expect(
+      screen.getByText("1960: 1681479人 (比率: 33.37%)")
+    ).toBeInTheDocument();
+  });
+
+  it("人口データの取得中にエラーメッセージが表示される", async () => {
+    (fetchPopulation as jest.Mock).mockRejectedValue(new Error("API Error"));
+
+    render(<PopulationSelector prefectures={mockPrefectures} />);
+
+    fireEvent.change(screen.getByRole("combobox"), { target: { value: "1" } });
+
+    await waitFor(() => screen.getByText(/人口データの取得に失敗しました/i));
+
+    expect(
+      screen.getByText(/人口データの取得に失敗しました/i)
+    ).toBeInTheDocument();
+  });
+});