diff --git a/.github/workflows/test_pull_requests.yml b/.github/workflows/test_pull_requests.yml
index ab5fd0330..2b8fe4542 100644
--- a/.github/workflows/test_pull_requests.yml
+++ b/.github/workflows/test_pull_requests.yml
@@ -18,25 +18,19 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-latest, macos-latest, windows-latest]
+        #os: [ubuntu-latest, macos-latest, windows-latest]
+        # macos > 13 has arm-based cpu and does not have pre-build
+        # wheel for scikit-image>=0.14.2,<0.17. Compiling from source
+        # not trivial.
+        os: [ubuntu-latest, macos-13, windows-latest]
         # see supported versions at
         # https://raw.githubusercontent.com/actions/python-versions/master/versions-manifest.json
-        python-version: [2.7, 3.5, 3.6, 3.7, 3.8]
-        # test only 2.7 and the latest 3.x on mac
+        python-version: [3.7, 3.8]
+        # test only the latest 3.x on mac
         # test only the latest 3.x on windows
         exclude:
-          - os: macos-latest
-            python-version: 3.5
-          - os: macos-latest
-            python-version: 3.6
-          - os: macos-latest
+          - os: macos-13
             python-version: 3.7
-          - os: windows-latest
-            python-version: 2.7  # causes a Shapely install error
-          - os: windows-latest
-            python-version: 3.5
-          - os: windows-latest
-            python-version: 3.6
           - os: windows-latest
             python-version: 3.7
     env:
@@ -103,27 +97,12 @@ jobs:
         restore-keys: |
           ${{ runner.os }}-pip-
 
-    # ----------------
-    # Install dependencies
-    # ----------------
-    - name: Install dependencies
-      run: |
-        pip install -r requirements.txt
-
-    - name: Install test dependencies
-      run: |
-        pip install --upgrade -r test/requirements.txt
-
-    - name: Install further test tools
-      run: |
-        pip install coverage pytest-cov flake8
-
     # ----------------
     # Install library
     # ----------------
     - name: Install library
       run: |
-        pip install .
+        pip install .[dev]
 
     # ----------------
     # Run checks and tests
diff --git a/requirements.txt b/requirements.txt
deleted file mode 100644
index 5bd6778e3..000000000
--- a/requirements.txt
+++ /dev/null
@@ -1,15 +0,0 @@
-six
-# The test for imgaug.augmenters.blend.blend_alpha() fails for numpy<1.15.
-# All other tests seemed to work as of 2019/01/04.
-numpy>=1.15
-scipy
-Pillow
-matplotlib
-scikit-image>=0.14.2,<0.18.2 # breaks random interface in imagecorruptions
-opencv-python-headless<4
-# imageio versions past 2.6.1 do not support <3.5 anymore
-imageio<=2.6.1; python_version<'3.5'
-imageio; python_version>='3.5'
-Shapely
-# numba is not available in <=3.5
-numba; python_version>='3.6'
diff --git a/setup.py b/setup.py
index b90f87c4a..ea7c52cdb 100644
--- a/setup.py
+++ b/setup.py
@@ -29,6 +29,9 @@
 DEV_REQUIRES = [
     "pytest-subtests",
     "xdoctest >= 0.7.2",
+    "coverage",
+    "pytest-cov",
+    "flake8",
 ]