public void FromConfiguration_HttpClientIsNull_ThrowsArgumentNullException()
{
var exception = Assert.Throws <ArgumentNullException>(() => HttpClientExtensions.FromConfiguration(null, null, ""));
Assert.Equal("client", exception.ParamName);
exception = Assert.Throws <ArgumentNullException>(() => HttpClientExtensions.FromConfiguration(null, "", null));
Assert.Equal("client", exception.ParamName);
}