improve contribute page

Author: ytdHuang

README.md

@@ -175,7 +175,7 @@ Here we provide a brief performance comparison between `QuantumToolbox.jl` and o
 
 You are most welcome to contribute to `QuantumToolbox.jl` development by forking this repository and sending pull requests (PRs), or filing bug reports at the issues page. You can also help out with users' questions, or discuss proposed changes in the [QuTiP discussion group](https://groups.google.com/g/qutip).
 
-For more information about contribution, including technical advice, please see the [Contributing to QuantumToolbox.jl](https://qutip.org/QuantumToolbox.jl/stable/resources/contributing) section of the documentation.
+For more information about contribution, including technical advice, please see the [Contributing to Quantum Toolbox in Julia](https://qutip.org/QuantumToolbox.jl/stable/resources/contributing).
 
 ## Acknowledgements
 

docs/src/resources/contributing.md

@@ -1,4 +1,4 @@
-# [Contributing to QuantumToolbox.jl](@id doc-Contribute)
+# [Contributing to Quantum Toolbox in Julia](@id doc-Contribute)
 
 ## [Quick Start](@id doc-Contribute:Quick-Start)
 
@@ -32,6 +32,12 @@ make test
 
 This command will automatically rebuild `Julia` and run the script located in `test/runtests.jl` (should cover both the original tests and the new test(s) you add).
 
+The tests are divided into several test groups, where the group names are defined in the file `test/runtests.jl` with a variable `GROUP`. One can also run the test scripts just for a certain test group by adding an argument `GROUP=<test-group-name>` to the `make test` command. For example, to run the tests for group `Core`, one can use the following command:
+
+```shell
+make GROUP=Core test
+```
+
 ## [Julia Code Format](@id doc-Contribute:Julia-Code-Format)
 
 We use [`JuliaFormatter.jl`](https://github.com/domluna/JuliaFormatter.jl) to format all the source codes. The code style and extra formatting options is defined in the file `.JuliaFormatter.toml` in the repository.