Trying to use TDD with C++ in VS 2019

Question

this is my first Question im asking on stackoverflow, so please don´t be too harsh on me. Warning... this also probably will be a noob question.

As an aspiring Software Developer with C++ in Visual Studio 2019, i want to add TDD to my Coding-Style. I used it with C# and the xUnit.net-Framework before without any problems at all, but C++ and GoogleTest don´t seem to like me.

What i did and where it prevents me from going forward:

1. I created the the Testproject within the solution with static libraries
2. Then i created the Test, let it run -> failed as expected
3. Created the class to be tested with its boolean Method "isPalindrom" (yes i am trying to get better with leetcode quests)
4. The error which i can´t seem to find the solution for occures LNK2019 and LNK1120

So i added the dependency of the project from the class to be tested to the testproject. And i added the folder, which contains the header and source files from the class to the external includes of the testproject.

What am i missing? Every help will be highly appreciated!

Solution Explorer: enter image description here

The Implementation: enter image description here

The Testmethod: enter image description here

The Errorlist: enter image description here