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Response Templating

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Stef Heyenrath edited this page May 29, 2024 · 27 revisions

Response headers and bodies can optionally be rendered (templated) with:

This enables attributes of the request to be used in generating the response e.g. to pass the value of a request ID header as a response header or render an identifier from part of the URL in the response body. To use this functionality, add .WithTransformer() to the response builder.

Way-Of-Working

1. Define "Handlebars template"

Hello {{firstname}}

2. Data

var user = new
{
  firstname = "Stef"
}

3. Result

Hello Stef

C# Example for using Handlebars.Net :

var server = WireMockServer.Start();
server
  .Given(
    Request.Create().WithPath("/some/thing").UsingGet()
  )
  .RespondWith(
    Response.Create()
      .WithBody("Hello world! Your path is {{request.path}}.")
      .WithTransformer()
  );

Mapping Json Example using Handlebars.Net:

{
    "Guid": "fd8ca21b-db82-48bc-ae5a-fc2153c2b0db",
    "Request": {
        "Path": {
            "Matchers": [
                {
                    "Name": "WildcardMatcher",
                    "Pattern": "/bodyasfile_transform123"
                }
            ]
        },
        "Methods": [
            "get"
        ]
    },
    "Response": {
        "Headers": { "Content-Type": "application/xml" },
        "BodyAsFile": "c:\\temp-wiremock\\__admin\\mappings\\_{{request.query.MyUniqueNumber}}_\\MyXmlResponse.xml",
    	"UseTransformer": true,
        "UseTransformerForBodyAsFile": true // ⭐
    }
}

Scriban

For using Scriban as templating engine, just provide the type:

C#

  // . . .
  .WithTransformer(TransformerType.Scriban) // or TransformerType.ScribanDotLiquid
  // . . .

JSON

{
    . . .
    "Response": {
        . . .
    	"UseTransformer": true,
        "TransformerType": "Scriban"
    }
}

Note

Scriban and Handlebars.Net are supported, however some functionality from Scriban cannot not (yet) be used in WireMock.Net, these topics are:

  • DOT notation for accessing this {{request.PathSegments.[0]}} does not work
  • WireMockList is not supported by Scriban

So the examples and explication below is mostly targeted to Handlebars.Net

The request model

The model of the request is supplied to the header and body templates. The following request attributes are available:

  • request.url - URL path and query
  • request.method - The HTTP method such as GET or POST.
  • request.protocol - The scheme such as http or https.
  • request.host - The name of the host in the URL.
  • request.origin - The base URL of the request which is equivalent to {Protocol}://{Host}:{Port}.
  • request.absoluteurl - URL path and query (absolute)
  • request.path - URL path
  • request.absolutepath - URL path (absolute)
  • request.PathSegments.[<n>] - URL path segment (zero indexed) e.g. request.PathSegments.[2]
  • request.AbsolutePathSegments.[<n>] - URL absolute path segments (zero indexed) e.g. request.AbsolutePathSegments.[2]
  • request.query.<key>- First value of a query parameter e.g. request.query.search
  • request.query.<key>.[<n>]- nth value of a query parameter (zero indexed) e.g. request.query.search.[5]
  • request.headers.<key> - First value of a request header e.g. request.headers.X-Request-Id
  • request.headers.[<key>] - Header with awkward characters e.g. request.headers.[$?blah]
  • request.headers.<key>.[<n>] - nth value of a header (zero indexed) e.g. request.headers.ManyThings.[1]
  • request.cookies.<key> - Value of a request cookie e.g. request.cookies.JSESSIONID
  • request.body - Request body text as string
  • request.bodyAsJson - Request body as dynamic Json Object. Note that the request must contain the header Content-Type with value application/json!

Transform the content from a referenced file

📝 By default, only the response (headers, statuscode, body) are transformed when the .WithTransformer() or UseTransformer are defined.

⭐ In case you also want to transform the contents from a referenced file (via BodyAsFile), an additional parameter need to added. Like .WithTransformer(bool) or UseTransformerForBodyAsFile = true. (#386 and #1106)

Standard Handlebars helpers

All of the standard helpers (template functions) provided by the C# Handlebars implementation are available.

Additional Handlebars helpers

In addition to the standard helpers, also the helpers from Handlebars.Net.Helpers are supported.

Extra WireMock.Net Handlebars helpers

The following extra helpers are present in WireMock.Net:

JsonPath

JsonPath support is also present (internal logic is based on Newtonsoft.Json).

Two functions are present:

  1. JsonPath.SelectToken
  2. JsonPath.SelectTokens

JsonPath.SelectToken

This can be used in C# like:

var server = WireMockServer.Start();
server
    .Given(Request.Create().WithPath("/jsonpathtestToken").UsingPost())
    .RespondWith(Response.Create()
        .WithHeader("Content-Type", "application/json")
        .WithBody("{{JsonPath.SelectToken request.body \"$.Manufacturers[?(@.Name == 'Acme Co')]\"}}")
        .WithTransformer()
    );

⚠️ When returning a more complex Json Body like this:

{
  "market": "{{JsonPath.SelectToken request.bodyAsJson '$.pricingContext.market'}}",
  "languages": "en"
}

You need to to use single quote (') instead of escaped double quotes (\") because of some parsing error @ Handlebars.Net (see also #1108).

Or using the admin mapping file:

{
    "Request": {
        "Path": {
            "Matchers": [
                {
                    "Name": "WildcardMatcher",
                    "Pattern": "/jsonpathtestToken"
                }
            ]
        },
        "Methods": [
            "post"
        ]
    },
    "Response": {
        "Body": "{{JsonPath.SelectToken request.body \"$.Manufacturers[?(@.Name == 'Acme Co')]\"}}",
        "UseTransformer": true,
        "Headers": {
            "Content-Type": "application/json"
        }
    }
}

Note that also replacing values in a Json Object and returning a the body as Json is supported, to use this, use a mapping file like this:

{
  "Request": {
    "Path": {
      "Matchers": [
        {
          "Name": "WildcardMatcher",
          "Pattern": "/test"
        }
      ]
    },
    "Methods": [
      "post"
    ]
  },
  "Response": {
    "BodyAsJson": {
      "path": "{{request.path}}",
      "result": "{{JsonPath.SelectToken request.bodyAsJson \"username\"}}"
    },
    "UseTransformer": true,
    "Headers": {
      "Content-Type": "application/json"
    }
  }
}

Random

It's possible to return random data using the Random Handlebars function.

Random Text

Example: to generate a random string between 8 and 20 characters, use this code in C#:

var server = WireMockServer.Start();
server
    .Given(Request.Create().WithPath("/random").UsingGet())
    .RespondWith(Response.Create()
        .WithHeader("Content-Type", "application/json")
        .WithBodyAsJson(
            Text = "{{Random Type=\"Text\" Min=8 Max=20}}",
        )
        .WithTransformer()
    );

Example: to generate a random string using a Regex pattern, use this code in C#:

var server = FluentMockServer.Start();
server
    .Given(Request.Create().WithPath("/random-regex").UsingGet())
    .RespondWith(Response.Create()
        .WithHeader("Content-Type", "application/json")
        .WithBodyAsJson(
            Text = "{{Xeger \"[1-9][0-9]{3}[A-Z]{2}\"}",
        )
        .WithTransformer()
    );

Random (all supported randomizers)

You can use the powerful Regular Expression string generator based on Fare - Finite Automata and Regular Expressions.

  • Text Regex Pattern: "{{Xeger Pattern=\"[1-9][0-9]{3}[A-Z]{2}"}}"

Besides a random text string, it's also possible to generate this random data:

  • Integer: "{{Random Type=\"Integer\" Min=100 Max=999}}"
  • Guid: "{{Random Type=\"Guid\"}}"
  • City: "{{Random Type=\"City\"}}"
  • Country: "{{Random Type=\"Country\"}}"
  • First Name: "{{Random Type=\"FirstName\" Male=false Female=true}}"
  • Email Address: "{{Random Type=\"EmailAddress\"}}"
  • Text Words: "{{Random Type=\"TextWords\" Min=10 Max=20}}"
  • Text Regex Pattern: "{{Random Type=\"TextRegex\" Pattern=\"[1-9][0-9]{3}[A-Z]{2}"}}"
  • Text Lorum Ipsum: "{{Random Type=\"TextIpsum\" Paragraphs=2}}"
  • String List: "{{Random Type=\"StringList\" Values=[\"a\", \"b\", \"c\"]}}"
  • IPv4 Address: "{{Random Type=\"IPv4Address\"}}"
  • IPv6 Address: "{{Random Type=\"IPv6Address\" Min = "0000:0001:0000:0000:0020:ff00:0042:8000", Max = "2001:0db8:0120:0000:0030:ff00:aa42:8329"}}"
  • MAC Address: "{{Random Type=\"MACAddress\"}}"
  • For more details on the supported random data types, see RandomDataGenerator.Net;

Note: instead of using \" in above examples, you can also use '.

XPath

XPath support is also present

Three functions are present:

  1. XPath.SelectSingleNode
  2. XPath.SelectNodes
  3. XPath.Evaluate

XPath.SelectSingleNode

This can be used in C# like:

var server = WireMockServer.Start();
server
    .Given(Request.Create().WithPath("/xpath1").UsingPost())
    .RespondWith(Response.Create()
        .WithHeader("Content-Type", "application/xml")
        .WithBody("<response>{{XPath.SelectSingleNode request.body \"/todo-list/todo-item[1]\"}}</response>")
        .WithTransformer()
    );

Or using the admin mapping file:

{
    "Request": {
        "Path": {
            "Matchers": [
                {
                    "Name": "WildcardMatcher",
                    "Pattern": "/xpath1"
                }
            ]
        },
        "Methods": [
            "post"
        ]
    },
    "Response": {
        "Body": "<response>{{XPath.SelectSingleNode request.body \"/todo-list/todo-item[1]\"}}</response>",
        "UseTransformer": true,
        "Headers": {
            "Content-Type": "application/xml"
        }
    }
}

For examples on XPath.SelectNodes and XPath.Evaluate, see https://github.com/WireMock-Net/WireMock.Net/blob/master/test/WireMock.Net.Tests/ResponseBuilders/ResponseWithHandlebarsXPathTests.cs

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