/******************************************************************************************
* Example 1: How it is normally done.
* This is bad because: hard to test, you depend on concrete classes and their details.
*******************************************************************************************/

public class HttpThing
{
    public async string GetResponseAsString()
    {
        ... //details
    }
}

public class ClientCode
{
    private HttpThing http = new() HttpThing;

    public string OperateWithResponse()
    {
        var thing = http.GetResponseAsString;
        // do something with thing
        return result;
    }
}

[Test]
public class TestClientCode
{
    [TestCase]
    public void TestOperateWithResponse()
    {
        // Now I have to initialize the whole thing if I want to test this code
        // and what if the response is different for whatever reason? What if I want to test and I don't have internet?
    }

}

/******************************************************************************************
* Example 2: How it could be.
* This is good because: Easy to test, you don't depend on details, it both has dependency injection and dependency inversion.
*******************************************************************************************/

public interface IHttpThing
{
    async string GetResponseAsString();
}

public class HttpThing: IHttpThing
{
    public async string GetResponseAsString()
    {
        //details, same as first example
    }
}

public class ClientCode
{
    private IHttpThing http;

    public ClientCode(IHttpThing http)
    {
        this.http = http;
    }

    public string OperateWithResponse()
    {
        var thing = http.GetResponseAsString;
        // do something with thing
        return result;
    }
}

public class MockHttpThing: IHttpThing
{
    public async string GetResponseAsString()
    {
        // I can set exactly what I expect to get
        return "{'something': [1, 2, 3], 'another_thing': true}"
    }
}

[Test]
public class TestClientCode
{
    public void TestOperationWithResponse()
    {
        var fakeHttp = new MockHttpThing();
        var client = new ClientCode(fakeHttp);
        // all my asserts and stuff that I can do in milisecond because I don't depend on anyone else.
    }
}