[pitivi] tests: Allow debugging unit tests

[Alexandru Băluț <alexbalut src gnome org>]

commit 977ef09fba7a592963ee39ffec9af3a831a4e83b
Author: Robert Dyer <rdyer unl edu>
Date:   Wed Apr 6 21:35:46 2022 +0000

    tests: Allow debugging unit tests
    
    Fixes #2604

 docs/Debugging.md      | 18 ++++++++++++++++++
 tests/common.py        | 12 ++++++++----
 tests/ptv_testsuite.py |  6 ++++++
 3 files changed, 32 insertions(+), 4 deletions(-)
---
diff --git a/docs/Debugging.md b/docs/Debugging.md
index d724fcc56..bf9cfed71 100644
--- a/docs/Debugging.md
+++ b/docs/Debugging.md
@@ -33,3 +33,21 @@ Waiting for the debugger to attach...
 ```
 
 Press `F5` in VS Code. If the Pitivi window shows up, your debugger is working.
+
+### Debugging Unit Tests
+
+You can also debug the unit tests by launching the test suite with the `PITIVI_VSCODE_DEBUG` environment 
variable set to 1:
+
+```
+(ptv-flatpak) $ PITIVI_VSCODE_DEBUG=1 ptvtests
+[...]
+Waiting for the debugger to attach...
+```
+
+Note the test suite typically limits how long a test can run and will kill any test reaching the timeout 
period.  Thus, when you set a breakpoint in a test, you may have to increase the timeouts to avoid it being 
killed while you debug:
+
+```
+(ptv-flatpak) $ PITIVI_VSCODE_DEBUG=1 ptvtests --timeout-factor 1000 [-t test_filename_or_method]
+[...]
+Waiting for the debugger to attach...
+```
diff --git a/tests/common.py b/tests/common.py
index 500f5e5ae..2a1ccb13f 100644
--- a/tests/common.py
+++ b/tests/common.py
@@ -154,13 +154,17 @@ def create_main_loop():
         mainloop.quit()
 
     def run(timeout_seconds=5, until_empty=False):
-        source = GLib.timeout_source_new_seconds(timeout_seconds)
-        source.set_callback(timeout_cb)
-        source.attach()
+        # Limit the test running time only when not debugging.
+        debugging = os.environ.get("PITIVI_VSCODE_DEBUG", False)
+        if not debugging:
+            source = GLib.timeout_source_new_seconds(timeout_seconds)
+            source.set_callback(timeout_cb)
+            source.attach()
         if until_empty:
             GLib.idle_add(mainloop.quit, priority=GLib.PRIORITY_LOW + 1)
         GLib.MainLoop.run(mainloop)
-        source.destroy()
+        if not debugging:
+            source.destroy()
         if timed_out:
             raise Exception("Timed out after %s seconds" % timeout_seconds)
 
diff --git a/tests/ptv_testsuite.py b/tests/ptv_testsuite.py
index a379e7c23..e11e9a8a3 100644
--- a/tests/ptv_testsuite.py
+++ b/tests/ptv_testsuite.py
@@ -42,6 +42,12 @@ class PitiviTest(Test):
 
 def setup_tests(test_manager, options):
     """Sets up Pitivi unit testsuite."""
+    if os.environ.get("PITIVI_VSCODE_DEBUG", False):
+        import debugpy
+        debugpy.listen(5678)
+        print("Waiting for the debugger to attach...")
+        debugpy.wait_for_client()
+
     loader = unittest.TestLoader()
     testsuites = loader.discover(CDIR)
     for testsuite in testsuites: