The code organization goes as follows:

• backend: Additional unified tensor interface for supported frameworks. The functions there are only used in unit tests, not DGL itself. Note that the code there are not unit tests by themselves.
• compute: All framework-agnostic computation-related unit tests go there.
• ${DGLBACKEND} (e.g. pytorch and mxnet): All framework-specific computation-related unit tests go there.
• graph_index: All unit tests for C++ graph structure implementation go there. The Python API being tested in this directory, if any, should be as minimal as possible (usually simple wrappers of corresponding C++ functions).
• lint: Pylint-related files.
• scripts: Automated test scripts for CI.

Compile with unittest by executing the command below

# Assume current directory is the root directory of dgl, and googletest submodule is initialized
mkdir build
cd build
cmake .. -DBUILD_CPP_TEST=1
make -j${nproc}
./runUnitTests