Automapper Dictionary Mapping Problem

Automapper.Tests.cs

using AutoMapper;
using FluentAssertions;
using System.Collections.Generic;
using Xunit;

namespace Reporter.Tests
{
    public class TestType
    {
        public string Prop1 { get; set; }
        public string Prop2 { get; set; }
    }

    public class TestClass<T> where T : new()
    {
        public TestClass()
        {
            Mapper.Initialize(cfg => cfg.CreateMap<Dictionary<string, string>, T>());
        }

        public T GetMappedObject(string prop1, string prop2)
        {
            return Mapper.Map<T>(new Dictionary<string, string>{
                { "Prop1", prop1 },
                { "Prop2", prop2 }
            });
        }
    }

    public class AutomapperTests
    {
        [Fact]
        public void TestMapping()
        {
            var mapper = new TestClass<TestType>();

            var result = mapper.GetMappedObject("value1", "value2");

            result.Prop1.Should().Be("value1");
            result.Prop2.Should().Be("value2");
        }
    }
}

AutomapperTests.csproj

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp1.1</TargetFramework>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.0.0"/>
    <PackageReference Include="xunit" Version="2.2.0"/>
    <PackageReference Include="xunit.runner.visualstudio" Version="2.2.0"/>
    <PackageReference Include="FakeItEasy" Version="3.4.2"/>
    <PackageReference Include="FluentAssertions" Version="4.19.3"/>
    <PackageReference Include="AutoMapper" Version="6.1.1"/>
  </ItemGroup>
  <ItemGroup>
    <Service Include="{82a7f48d-3b50-4b1e-b82e-3ada8210c358}"/>
  </ItemGroup>
</Project>