diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index faff507..cd2ba29 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -48,9 +48,6 @@ jobs:
         run: |
           micromamba activate pyjs-wasm
 
-          python -m pip install git+https://github.com/emscripten-forge/empack@rootpack                       --no-deps --ignore-installed
-          python -m pip install git+https://github.com/DerThorsten/pyjs-code-runner@relocate_env              --no-deps --ignore-installed
-
           emsdk activate ${{matrix.emsdk_ver}}
           source $CONDA_EMSDK_DIR/emsdk_env.sh
 
@@ -59,7 +56,7 @@ jobs:
             -c https://repo.mamba.pm/emscripten-forge \
             -c https://repo.mamba.pm/conda-forge \
             --yes \
-            python pybind11 nlohmann_json pybind11_json numpy pytest bzip2 sqlite zlib libffi
+            python pybind11 nlohmann_json pybind11_json numpy "pytest==7.1.1" bzip2 sqlite zlib libffi exceptiongroup
 
 
           mkdir build
@@ -94,7 +91,7 @@ jobs:
             -c https://repo.mamba.pm/emscripten-forge \
             -c https://repo.mamba.pm/conda-forge \
             --yes \
-            python pytest numpy
+            python "pytest==7.1.1" numpy exceptiongroup
 
 
       - name: Test in browser-main
@@ -133,7 +130,7 @@ jobs:
             -c https://repo.mamba.pm/emscripten-forge \
             -c https://repo.mamba.pm/conda-forge \
             --yes \
-            python pytest
+            python "pytest==7.1.1" exceptiongroup
 
       - name: Test in browser-main-no-numpy
         run: |
diff --git a/environment-dev.yml b/environment-dev.yml
index 4c5f69f..a73c37b 100644
--- a/environment-dev.yml
+++ b/environment-dev.yml
@@ -7,9 +7,10 @@ dependencies:
   - python=3.10
   - yarn
   - click
+  - empack >=3.0.1
   - emsdk >=3.1.11
-  - empack >=1.1.0
   - microsoft::playwright
   - ninja
   - nodejs >= 18.7.0
-  - pyjs_code_runner == 1.1.0
\ No newline at end of file
+  - pyjs_code_runner >= 2.0.1
+  - exceptiongroup
\ No newline at end of file
diff --git a/include/pyjs/pre_js/init.js b/include/pyjs/pre_js/init.js
index 13948c2..96f530e 100644
--- a/include/pyjs/pre_js/init.js
+++ b/include/pyjs/pre_js/init.js
@@ -176,15 +176,22 @@ _add_resolve_done_callback
 
     Module._is_initialized = true
 
-//     Module.exec(`
-// import sys
-// import sysconfig
-// side_path = "${side_path}"
-// from pathlib import Path
-// Path(side_path).mkdir(parents=True, exist_ok=True)
-// if True and side_path not in sys.path:
-//     sys.path.append(side_path)
-// `)
+    // make sure time.sleep is working
+    Module.exec(`
+import time
+def _mock_time_sleep():
+    def sleep(seconds):
+        """Delay execution for a given number of seconds.  The argument may be
+        a floating point number for subsecond precision.
+        """
+        start = now = time.time()
+        while now - start < seconds:
+            now = time.time()
+
+    time.sleep = sleep
+_mock_time_sleep()
+del _mock_time_sleep
+`)
 
     return p
 
diff --git a/tests/tests/test_pyjs.py b/tests/tests/test_pyjs.py
index 66b90aa..faa0df9 100644
--- a/tests/tests/test_pyjs.py
+++ b/tests/tests/test_pyjs.py
@@ -554,3 +554,17 @@ def test_int_container():
     js_obj = jsf()
     py_obj = pyjs.to_py(js_obj)
     assert py_obj
+
+
+
+def test_sleep():
+    import time
+    start = time.time()
+    time.sleep(2)
+    end = time.time()
+
+    assert end - start >= 2
+
+    # probably we can also do more precise tests
+    # but lets keept it simple for now
+    assert end - start < 2.1
\ No newline at end of file