Question: Does the WireMock send Content-Length response header #102

New Issue

adam · 2025-12-29T08:22:18+01:00

adam commented

2025-12-29 08:22:18 +01:00

Originally created by @o7g8 on GitHub (May 16, 2018).

Hello,

I need to make a response mock with a specific value of Content-Length header:

        [TestMethod]
        public async Task CheckMockHeaders() {
            var responseBody = @"<?xml version=""1.0""?><empty/>";
            mockServer
                .Given(Request
                    .Create()
                    .WithPath("/test")
                    .UsingPost())
                .RespondWith(Response
                    .Create()
                    .WithStatusCode(200)
                    .WithHeader("content-type", "text/xml")
                    .WithHeader("Content-Length", responseBody.Length.ToString())
                    .WithBody(responseBody));
            
            using (var httpClient = new HttpClient()) {
                var uri = mockServer.Urls.Single() + "test";
                using (var response = await httpClient.PostAsync(uri, new StringContent(""))) {
                    response.EnsureSuccessStatusCode();
                    Assert.IsTrue(response.Content.Headers.Any(x => x.Key == "Content-Length"));
                }
            }
        }

Unfortunately the Assert fails and the Content-Length is not part of response.Content.Headers.

I suspect problem might be in the fact that the server by default assigns header Transfer-Encoding: chunked.

According to https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Transfer-Encoding

Data is sent in a series of chunks. The Content-Length header is omitted in this case and at the beginning of each chunk you need to add the length of the current chunk in hexadecimal format...

I was not able to assign my own Transfer-Encoding: identity. I will create a separate question about it.

WireMock.Net version 1.0.3.16.

Originally created by @o7g8 on GitHub (May 16, 2018). Hello, I need to make a response mock with a specific value of `Content-Length` header: ```csharp [TestMethod] public async Task CheckMockHeaders() { var responseBody = @"<?xml version=""1.0""?><empty/>"; mockServer .Given(Request .Create() .WithPath("/test") .UsingPost()) .RespondWith(Response .Create() .WithStatusCode(200) .WithHeader("content-type", "text/xml") .WithHeader("Content-Length", responseBody.Length.ToString()) .WithBody(responseBody)); using (var httpClient = new HttpClient()) { var uri = mockServer.Urls.Single() + "test"; using (var response = await httpClient.PostAsync(uri, new StringContent(""))) { response.EnsureSuccessStatusCode(); Assert.IsTrue(response.Content.Headers.Any(x => x.Key == "Content-Length")); } } } ``` Unfortunately the Assert fails and the `Content-Length` is not part of `response.Content.Headers`. I suspect problem might be in the fact that the server by default assigns header `Transfer-Encoding: chunked`. According to https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Transfer-Encoding > Data is sent in a series of chunks. The Content-Length header is omitted in this case and at the beginning of each chunk you need to add the length of the current chunk in hexadecimal format... I was not able to assign my own `Transfer-Encoding: identity`. I will create a separate question about it. WireMock.Net version `1.0.3.16`.

adam closed this issue

2025-12-29 08:22:18 +01:00

adam commented

2025-12-29 08:22:18 +01:00

@StefH commented on GitHub (May 16, 2018):

For now I ignore these restricted headers in WireMock.Net:

Accept
Connection
ContentLength
ContentType
Date
Expect
Host
IfModifiedSince
KeepAlive
Range
Referer
TransferEncoding
UserAgent
ProxyConnection
WWWAuthenticate

See also https://msdn.microsoft.com/en-us/library/78h415ay(v=vs.110).aspx

Did you check the original java implementation from WireMock to see if this is possible there?

@StefH commented on GitHub (May 16, 2018): For now I ignore these restricted headers in WireMock.Net: - Accept - Connection - ContentLength - ContentType - Date - Expect - Host - IfModifiedSince - KeepAlive - Range - Referer - TransferEncoding - UserAgent - ProxyConnection - WWWAuthenticate See also https://msdn.microsoft.com/en-us/library/78h415ay(v=vs.110).aspx Did you check the original java implementation from WireMock to see if this is possible there?

adam commented

2025-12-29 08:22:19 +01:00

@o7g8 commented on GitHub (May 17, 2018):

I haven't checked the Java implementation, so I don't know if it's possible there.
Regarding the https://msdn.microsoft.com/en-us/library/78h415ay(v=vs.110).aspx it says:

Tests whether the specified HTTP header can be set for the request.

But in my example, I attempt to set the Content-Length for the response, while WebHeaderCollection.IsRestricted concerns about requests.

The purpose of WireMock is to allow people to mock service responses, therefore, in my opinion, it's fair to expect that the library allows building a response with any kind of content.
The user may even want to build mocks with a wrong combination and/or content of response headers in order to test client's robustness.

Another thing which I have noticed inspecting the internals of mockServer: despite the Content-Length is not part of the actual response, the header is registered in the 'response' part of the server's logs. I think it's inconsistent behavior - the logs should reflect reality.

I also think that if WireMock has its own ideas about allowed and not allowed request and response headers, their content and their combinations, the server should crash in the case when the inconsistency is detected instead of silently ignoring it.

If we get back to my example: when you read the Given-RepondWith section you get an impression that the response does contain the Content-Length header, but in reality, it doesn't. And you won't notice it unless you check for it specifically. But I think you will agree that double checking of mocks/stabs state is not a best practice in tests.

@o7g8 commented on GitHub (May 17, 2018): I haven't checked the Java implementation, so I don't know if it's possible there. Regarding the https://msdn.microsoft.com/en-us/library/78h415ay(v=vs.110).aspx it says: > Tests whether the specified HTTP header can be set for the request. But in my example, I attempt to set the `Content-Length` for the _response_, while `WebHeaderCollection.IsRestricted` concerns about _requests_. The purpose of WireMock is to allow people to mock service responses, therefore, in my opinion, it's fair to expect that the library allows building a response with any kind of content. The user may even want to build mocks with a wrong combination and/or content of response headers in order to test client's robustness. Another thing which I have noticed inspecting the internals of `mockServer`: despite the `Content-Length` is not part of the actual response, the header is registered in the 'response' part of the server's logs. I think it's inconsistent behavior - the logs should reflect reality. I also think that if WireMock has its own ideas about allowed and not allowed request and response headers, their content and their combinations, the server should crash in the case when the inconsistency is detected instead of silently ignoring it. If we get back to my example: when you read the `Given-RepondWith` section you get an impression that the response _does_ contain the `Content-Length` header, but in reality, it doesn't. And you won't notice it unless you check for it specifically. But I think you will agree that double checking of mocks/stabs state is not a best practice in tests.

adam commented

2025-12-29 08:22:19 +01:00

@StefH commented on GitHub (May 17, 2018):

You are correct. I think that I switched Request en Response headers in my implementation.

I had some troubles some time ago when setting the Content-Length header on the IOwinResponse or HttpResponse object.

I will check that code again, and keep you informed.

@StefH commented on GitHub (May 17, 2018): You are correct. I think that I switched Request en Response headers in my implementation. I had some troubles some time ago when setting the `Content-Length` header on the `IOwinResponse` or `HttpResponse` object. I will check that code again, and keep you informed.

adam commented

2025-12-29 08:22:19 +01:00

@StefH commented on GitHub (May 19, 2018):

I've created a PR : you take a look and review this : https://github.com/WireMock-Net/WireMock.Net/pull/142

@StefH commented on GitHub (May 19, 2018): I've created a PR : you take a look and review this : https://github.com/WireMock-Net/WireMock.Net/pull/142

adam commented

2025-12-29 08:22:19 +01:00

@StefH commented on GitHub (May 25, 2018):

Solved, see NuGet 1.0.3.18

@StefH commented on GitHub (May 25, 2018): Solved, see NuGet 1.0.3.18

adam referenced this issue

2025-12-29 08:33:28 +01:00

[PR #102] [MERGED] Feature: add WithBody(req => dostuff) style callback #767

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Reference: starred/WireMock.Net#102