32. Network Interception, Mock Responses & Fault Injection

Mocking Backend APIs with page.route

// Mock 500 internal server error on checkout:
page.route("/api/checkout", route -> {
    route.fulfill(new Route.FulfillOptions()
        .setStatus(500)
        .setContentType("application/json")
        .setBody("{"error": "Payment gateway unavailable"}"));
});
// Abort third-party tracking scripts to speed up tests:
page.route("/*analytics.js", Route::abort);
// Modify response headers:
page.route("**/api/user", route -> {
    route.resume(); // Pass through normally
});