diff --git a/.gitignore b/.gitignore
index e35d885..6a163a6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 _build
+.DS_Store
\ No newline at end of file
diff --git a/_toc.yml b/_toc.yml
index 6633a52..21e01cf 100644
--- a/_toc.yml
+++ b/_toc.yml
@@ -9,4 +9,5 @@ chapters:
 - file: what-is-quisp
 - file: getting-started
 - file: vscode
+- file: debugger
 
diff --git a/debugger.md b/debugger.md
new file mode 100644
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--- /dev/null
+++ b/debugger.md
@@ -0,0 +1,33 @@
+# Introduction to Visual Studio Code Debugger
+
+As we suggested you to use VSCode to develop QuiSP, we would like to introduce how you can use VSCode Debugger to debug the unit-tests and the simulation tests.
+
+## Caution
+
+Everytime you start a debug session, you should make sure that you have compiled QuiSP.  
+It is a common mistake to start a debug session without compiling your edits.  
+Before unit-tests, you need to compile QuiSP with `make run-unit-test MODE=debug`.  
+Before simulation tests, you need to compile QuiSP with `make exe MODE=debug`.  
+
+## All you need to know to debug
+
+By default, the configurations for the unit-tests and the simulation tests are done for you already.  
+To start the debug session, follow these steps:
+
+1. Select the **Run and Debug** icon in the **Activity Bar** on the side of VSCode.
+2. Next to the top left of the window, select either **UnitTests** or **Simulation** and click the green play button.  
+3. If you have breakpoints set in the QuiSP files, the debugger will stop at the breakpoints and you will be able to inspect the data at that point.  
+
+If you are unfamiliar with VSCode Debugger and want more detailed info, please refer to [this article](https://code.visualstudio.com/docs/editor/debugging)
+
+## Additional tips on debugging unit-tests
+
+When you debug UnitTests according to the previous section, the debug session will run the entire unit-tests in QuiSP.  
+It is also possible to debug one test at a time using the C++ TestMate extension, which is preinstalled in the QuiSP Dev Container.
+
+1. From the **Activity Bar**, select the **Testing** icon. Let's say you want to start the debug session for `Init_IsNotInitiator` of `AppTest` group.  
+2. In the **Testing** tab that you just opened, open TestMate C++, run_unit_test, and then AppTest.
+3. Under the AppTest, there should be several unit-tests that belong to the `AppTest` group. One of them is the `Init_IsNotInitiator` test.  
+4. Its debug session can be started once you hover over `Init_IsNotInitiator` and click the play button **Debug Test**.
+
+In the same way, you can pick other tests and start the debug session.