HttpTestUtils contains some classes which make it easier to mock out dependencies on HttpClient during unit-tests.
When code has a dependency on HttpClient it might be hard to test that code since in a unit-test you clearly do not want to send real HTTP messages. The HttpClientMock allows you to predefine the behaviour that must be executed by the HttpClient class.
Have a look at the HttpClientMockTests in the HttpTestUtils.Tests project to find out how to make use of it.