Unit Testing Generic Handlers - asp.net

Question

How can i test return value of "ProcessRequest" method in a generic handler with unit Test?
public class Handler1 : IHttpHandler
{
public void ProcessRequest(HttpContext context)
{
context.Response.ContentType = "text/plain";
context.Response.Write("Hello World");
}
public bool IsReusable
{
get
{
return false;
}
}
}

Answer 1

Instead of using mock, try to create test HttpContext with SimpleWorkerRequest like this:
SimpleWorkerRequest testRequest = new SimpleWorkerRequest("","","", null, new StringWriter());
HttpContext testContext = new HttpContext(testRequest);
HttpContext.Current = testContext;
Then you could create your handler and provide testContext to the ProcessRequest method:
var handler = new Handler1();
handler.ProcessRequest(testContext);
Then you could check HttpContext.Current.Response to make assertion about your test.
UPDATE:
I am attaching the full example of working unit-test(implementation of OutputFilterStream was taken from here):
[TestFixture]
[Category("Unit")]
public class WhenProcessingRequest
{
public class Handler1 : IHttpHandler
{
public void ProcessRequest(HttpContext context)
{
context.Response.ContentType = "text/plain";
context.Response.Write("Hello World");
}
public bool IsReusable
{
get
{
return false;
}
}
}
public class OutputFilterStream : Stream
{
private readonly Stream InnerStream;
private readonly MemoryStream CopyStream;
public OutputFilterStream(Stream inner)
{
this.InnerStream = inner;
this.CopyStream = new MemoryStream();
}
public string ReadStream()
{
lock (this.InnerStream)
{
if (this.CopyStream.Length <= 0L ||
!this.CopyStream.CanRead ||
!this.CopyStream.CanSeek)
{
return String.Empty;
}
long pos = this.CopyStream.Position;
this.CopyStream.Position = 0L;
try
{
return new StreamReader(this.CopyStream).ReadToEnd();
}
finally
{
try
{
this.CopyStream.Position = pos;
}
catch { }
}
}
}
public override bool CanRead
{
get { return this.InnerStream.CanRead; }
}
public override bool CanSeek
{
get { return this.InnerStream.CanSeek; }
}
public override bool CanWrite
{
get { return this.InnerStream.CanWrite; }
}
public override void Flush()
{
this.InnerStream.Flush();
}
public override long Length
{
get { return this.InnerStream.Length; }
}
public override long Position
{
get { return this.InnerStream.Position; }
set { this.CopyStream.Position = this.InnerStream.Position = value; }
}
public override int Read(byte[] buffer, int offset, int count)
{
return this.InnerStream.Read(buffer, offset, count);
}
public override long Seek(long offset, SeekOrigin origin)
{
this.CopyStream.Seek(offset, origin);
return this.InnerStream.Seek(offset, origin);
}
public override void SetLength(long value)
{
this.CopyStream.SetLength(value);
this.InnerStream.SetLength(value);
}
public override void Write(byte[] buffer, int offset, int count)
{
this.CopyStream.Write(buffer, offset, count);
this.InnerStream.Write(buffer, offset, count);
}
}
[Test]
public void should_write_response()
{
//arrange
SimpleWorkerRequest testRequest = new SimpleWorkerRequest("", "", "", null, new StringWriter());
HttpContext testContext = new HttpContext(testRequest);
testContext.Response.Filter = new OutputFilterStream(testContext.Response.Filter);
//act
var handler = new Handler1();
handler.ProcessRequest(testContext);
testContext.Response.End();//end request here(if it is not done in your Handler1)
//assert
var result = ((OutputFilterStream)testContext.Response.Filter).ReadStream();
Assert.AreEqual("Hello World", result);
}
}