Hello team,
I need some advice regarding IoT file download using Rest Client. Is it possible to download a file using OOB functionality of the Rest Client? They have exposed the file through GET - Serves files directly from a mounted directory over HTTP, so MES can retrieve a specific file by name without needing SFTP access.
In order to simulate this for automation testing, what would need to be done in order to host a file with a mock Rest Server?
I came across the documentation for the Rest server(Rest Server - Critical Manufacturing Developer Portal) and Mock MES instance(Connecting to a Live MES - Critical Manufacturing Developer Portal) and received confirmation from CMGPT that setting this up is possible using the steps outlined below. I would like to kindly seek your confirmation if these steps are correct.
Possible answer:
Yes, it is possible — the IoT Test Orchestrator’s Rest Server Simulator Plugin (RestServer.PluginMain) is the OOTB mechanism to host a mock HTTP server that serves files over GET for automation testing.- The plugin is powered by WireMock, supports registering GET endpoints via
restSimulator.Register(), and returns file content through aSystemReply(200, fileContent). - The mock server address/port is injected into the MES dataflow JSON so the REST Client driver targets it instead of the real external system.
The Right Tool — Rest Server Simulator Plugin
A Simulator Plugin mirrors the implementation of its corresponding automation protocol. Since the MES uses a REST Client driver to retrieve files, a REST Client requires a REST Server simulator. The IoT Test Orchestrator Framework provides exactly this with the dedicated Rest Server simulator plugin
Steps:
- Add the Rest Server simulator plugin to the test scenario configuration
- Register a GET endpoint that returns the file content as
SystemReply - Read the file from disk in the test and return it in the handler
- Configure the Rest Client driver in MES to point to the mock server address
Step-by-Step Setup
Step 1 — Add the Rest Server Plugin to the Scenario Configuration
To add the Rest Server simulator plugin to a test scenario, include its configuration in ScenarioConfiguration:
var port = new Random().Next(5000, 30000); // randomize to avoid concurrency collisions
var configuration = new ScenarioConfiguration()
.ManagerId("Manager01")
// ... other settings ...
.AddSimulatorPlugin<RestServer.PluginMain>(new RestServer.Plugin.SettingsBuilder()
.Address("http://localhost", port)
.ServerSettings(new WireMock.Settings.WireMockServerSettings()
{
StartAdminInterface = true
})
.Build())
.Build();
The Rest Server configuration properties are:
| Property | Type | Description | Default | |
|---|---|---|---|---|
Address |
string | Address | — | |
Port |
int | Port | 8080 | |
WireMockServerSettings |
object | Server Settings | — | 3 |
Step 2 — Register a GET Endpoint That Serves the File
Inside your test, retrieve the Rest Server simulator and register a GET endpoint that reads and returns the file content:
var restSimulator = (RestServer.PluginMain) context.Simulators["RestServer"];
// Read the file content from disk
var fileBytes = File.ReadAllBytes("path/to/your/testfile.csv");
var fileContent = Convert.ToBase64String(fileBytes); // or return as string if text
restSimulator.Register("/files/myfile.csv", (ISystemRequest request) =>
{
// Return the file with HTTP 200 and appropriate content
return new SystemReply(200, System.Text.Encoding.UTF8.GetString(fileBytes));
}, Common.Objects.Rest.RestVerb.Get);
The OOTB usage example for the Rest Server plugin shows registering a GET endpoint with restSimulator.Register(), providing the route, a handler lambda that returns a SystemReply(statusCode, body), and the HTTP verb.
Step 3 — Point the MES REST Client Driver to the Mock Server
In the Mock MES configuration, update the restMasterDataPath JSON to use the dynamically assigned port so the Rest Client driver targets the mock server address:
// Update the dataflow JSON to use the selected port
File.WriteAllText(
restMasterDataPath,
File.ReadAllText(restMasterDataPath).Replace("5000", port.ToString())
);
This ensures the MES REST Client in the workflow sends its GET /files/myfile.csv request to the mock server instead of the real external system.
Step 4 — Verify the File Was Requested
var fileWasRequested = false;
restSimulator.Register("/files/myfile.csv", (ISystemRequest request) =>
{
fileWasRequested = true;
var fileBytes = File.ReadAllBytes("path/to/testfile.csv");
return new SystemReply(200, System.Text.Encoding.UTF8.GetString(fileBytes));
}, Common.Objects.Rest.RestVerb.Get);
// ... trigger the MES workflow ...
scenario.Utilities.WaitFor(50, "File was never requested", () => fileWasRequested);
Thank You.