ci: build rust module in nix tests and run API tests in matrix

Author: tzanko-matev

.agents/tasks/2025/08/14-1027-initial-python-api

@@ -1,3 +1,5 @@
 Implement the Python API described in the design document for the Rust-based module. Write tests. Don't actually implement tracing using `runtime_tracing` yet, just add placeholders.
 --- FOLLOW UP TASK ---
-Implement the Python API described in the design document for the Rust-based module. Write tests. Don't actually implement tracing using runtime_tracing yet, just add placeholders.
+Implement the Python API described in the design document for the Rust-based module. Write tests. Don't actually implement tracing using runtime_tracing yet, just add placeholders.
+--- FOLLOW UP TASK ---
+The nix-tests task fails, because we haven't compiled the Rust module. The matrix rust tests currently don't run the new test, but they should.

.github/workflows/ci.yml

@@ -17,8 +17,8 @@ jobs:
           nix_path: nixpkgs=channel:nixos-25.05
           extra_nix_config: |
             experimental-features = nix-command flakes
-      - name: Run tests via Nix
-        run: nix develop --command just test
+      - name: Build Rust module and run tests via Nix
+        run: nix develop --command bash -lc 'just build-rust && .venv/bin/python -m unittest discover -v'
 
   rust-tests:
     name: Rust module test on ${{ matrix.os }} (Python ${{ matrix.python-version }})
@@ -43,4 +43,5 @@ jobs:
           v=${{matrix.python-version}}
           file=(crates/codetracer-python-recorder/target/wheels/*.whl)
           file="${file[0]}"
-          uv run -p python3.$v --with "${file}" --with pytest -- python -m pytest crates/codetracer-python-recorder/test -q
+          uv run -p python3.$v --with "${file}" --with pytest -- \
+            python -m pytest crates/codetracer-python-recorder/test tests/test_codetracer_api.py -q