devfront 테스트 커버리지 추가 보강

devfront/src/components/ui/copy-button.test.tsx

@@ -79,4 +79,29 @@ describe("CopyButton", () => {
     expect(execCommand).toHaveBeenCalledWith("copy");
     expect(onCopy).toHaveBeenCalledTimes(1);
   });
+
+  it("keeps running when the fallback copy flow fails", async () => {
+    const execCommand = vi.fn(() => false);
+    const errorSpy = vi.spyOn(console, "error").mockImplementation(() => {});
+    Object.defineProperty(document, "execCommand", {
+      value: execCommand,
+      configurable: true,
+    });
+    Object.defineProperty(window, "isSecureContext", {
+      value: false,
+      configurable: true,
+    });
+
+    const { container, onCopy } = renderCopyButton("client-secret");
+    const button = container.querySelector("button");
+    expect(button).not.toBeNull();
+
+    await act(async () => {
+      button?.dispatchEvent(new MouseEvent("click", { bubbles: true }));
+    });
+
+    expect(execCommand).toHaveBeenCalledWith("copy");
+    expect(onCopy).not.toHaveBeenCalled();
+    expect(errorSpy).toHaveBeenCalled();
+  });
 });