Simulate slow API responses

At a glance
Goal: Add artificial latency to API responses for testing
Time: 5 minutes
Plugins: LatencyPlugin
Prerequisites: Set up Dev Proxy

Dev Proxy allows you to simulate slow API responses by using the LatencyPlugin.

Start, by enabling the plugin in your Dev Proxy configuration file:

File: devproxyrc.json

{
  "$schema": "https://raw.githubusercontent.com/dotnet/dev-proxy/main/schemas/v2.0.0/rc.schema.json",
  "plugins": [
    {
      "name": "LatencyPlugin",
      "enabled": true,
      "pluginPath": "~appFolder/plugins/DevProxy.Plugins.dll",
      "configSection": "latencyPlugin"
    }
  ],
  "urlsToWatch": []
}

Next, specify the minimum and maximum delay (in milliseconds) to simulate for your API.

File: devproxyrc.json

"latencyPlugin": {
  "minMs": 200,
  "maxMs": 10000
}

The complete configuration file looks like this.

File: devproxyrc.json

{
  "$schema": "https://raw.githubusercontent.com/dotnet/dev-proxy/main/schemas/v2.0.0/rc.schema.json",
  "plugins": [
    {
      "name": "LatencyPlugin",
      "enabled": true,
      "pluginPath": "~appFolder/plugins/DevProxy.Plugins.dll",
      "configSection": "latencyPlugin"
    }
  ],
  "urlsToWatch": [
    "https://api.example.com/*"
  ],
  "latencyPlugin": {
    "$schema": "https://raw.githubusercontent.com/dotnet/dev-proxy/main/schemas/v2.0.0/latencyplugin.schema.json",
    "minMs": 200,
    "maxMs": 10000
  }
}

When a response is delayed, Dev Proxy displays the total duration it was delayed for in the console output.

See also

• LatencyPlugin - Full reference
• Test my app with random errors - Simulate API failures
• Glossary - Dev Proxy terminology