C++ unit test: "unresolved external symbol"

I've created a new solution in Rider and selected "Unit Test Project" in the wizard.  I named the solution "TestExample" and its project "Tests".  In this solution, I created a second project and selected "Library" (type: "Dynamic Library") in the wizard.  I named the second project "Sut".  So, now I have one solution "TestExample" containing two projects: "Tests" (which will contain the tests) and "Sut" (which will contain code that I would like to use in the tests).

No matter what I try, I can't convince Rider to successfully run tests in "TestExample" that use things from "Sut".

I modified the file "test.cpp" from project "TestExample" so that it contains the following:

#include "../Sut/NumberGetter.h"
#include "gtest/gtest.h"

TEST(TestCaseName, TestName)
{
  EXPECT_EQ(11, get_number());
}

I created a file named "NumberGetter.cpp" in project "Sut" with the following contents:

#include "NumberGetter.h"

int get_number()
{
  return 11;
}

I created a file named "NumberGetter.h" in project "Sut" with the following contents:

#pragma once

int get_number();

At this point, I tried to run the test by left-clicking on the run icon to the left of the test in file "test.cpp", but I got the following error:

  unresolved external symbol "int __cdecl get_number(void)" (?get_number@@YAHXZ) referenced in function "private: virtual void __cdecl TestCaseName_TestName_Test::TestBody(void)" (?TestBody@TestCaseName_TestName_Test@@EEAAXXZ)

Hoping to resolve this, I added the "Sut" project as a reference to the "Tests" project (right-click on the "Tests" project, select "Add... > Reference", check the box next to "Sut", then select "Add") and tried again.  However, now it errors out with:

  Microsoft.CppCommon.targets(1096, 5): [MSB6006] "link.exe" exited with code 1104.
  cannot open file 'C:\vs-ws\TestExample\x64\Debug\Sut.lib'

What am I doing wrong?  It works fine if I add the "NumberGetter.h" and "NumberGetter.cpp" files directly to the "Tests" project. However, if that's how it's supposed to be done, then I don't really understand why Rider gives you the choice to add a "Unit Test Project" in the new project wizard.  If one has authored a "Library" type project, then how does one add unit tests to it?

I've read the Rider tutorials, browsed places like YouTube, and done various Internet searches.  I'd really appreciate it if somebody could point me in the right direction.  Thank you in advance!