Core Render Pipeline error (Unity 2019)

I've suddenly started getting a series of errors in my project related to the Core Render Pipeline. I haven't added/removed any plugins or assets in my project.

Errors:

1.
Library\PackageCache\com.unity.render-pipelines.core@7.1.2\Tests\Runtime\RuntimeExampleTest.cs(2,19): error CS0234: The type or namespace name 'TestTools' does not exist in the namespace 'UnityEngine' (are you missing an assembly reference?)

2.
Library\PackageCache\com.unity.render-pipelines.core@7.1.2\Tests\Runtime\RuntimeExampleTest.cs(3,7): error CS0246: The type or namespace name 'NUnit' could not be found (are you missing a using directive or an assembly reference?)

3.
Library\PackageCache\com.unity.render-pipelines.core@7.1.2\Tests\Runtime\RuntimeExampleTest.cs(8,3): error CS0246: The type or namespace name 'TestAttribute' could not be found (are you missing a using directive or an assembly reference?)

4.
Library\PackageCache\com.unity.render-pipelines.core@7.1.2\Tests\Runtime\RuntimeExampleTest.cs(8,3): error CS0246: The type or namespace name 'Test' could not be found (are you missing a using directive or an assembly reference?)

5.
Library\PackageCache\com.unity.render-pipelines.core@7.1.2\Tests\Runtime\RuntimeExampleTest.cs(15,3): error CS0246: The type or namespace name 'UnityTestAttribute' could not be found (are you missing a using directive or an assembly reference?)

6.
Library\PackageCache\com.unity.render-pipelines.core@7.1.2\Tests\Runtime\RuntimeExampleTest.cs(15,3): error CS0246: The type or namespace name 'UnityTest' could not be found (are you missing a using directive or an assembly reference?)

I've tried:
- Removing the Library\PackageCache\com.unity.render-pipelines.core@7.1.2\Tests folder which threw a lot more errors (so I put it back)
- Reimporting assets for the entire project
- Removing and re-adding the VFX Graph through the package manager

Version info:
Unity 2019.1.4f1

What info can I provide to help troubleshoot? Thank you.

 

Im having the same problem