Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires contao/test-case 4.x-dev, found contao/test-case[1.0.0, ..., 1.6.0, 2.0.0, 2.1.0, 3.0.0, 3.1.0, 4.0.0, ..., 4.13.x-dev, 5.0.0-RC1, ..., 5.x-dev] but it does not match the constraint.

Process completed with exit code 2.