Mass replacing the common code of all tests
```
echo "Fixing $1"
ed "$1" <<'EOF'
1,/Testing/d
i
from render_layer_common import *
import unittest
import os
import sys
sys.path.append(os.path.dirname(__file__))
.
w
q
EOF
```
Using line-width of 120
test_evaluation_visibility_a failed before, but it is now fixed
test_evaluation_visibility_b passed before and was used as control to make sure it was not broken
