[Tests] Added new tests.
[Tests] Added some tests, modified others.
[Tests] Added test for data-grid.
[Tests] Changed some tests.
[Tests/data-grid] Fixed/Extended tests. Made method- and var-names of data-grid more clear.
[Tests] Changed assigment of root-vars to be more reliable.
[Tests] Fixed old tests and began new ones.
[Tests] Extended tests.