try to run with git-bash on windows

.github/workflows/test.yml

@@ -16,6 +16,7 @@ jobs:
         os:
           - ubuntu-latest
           - macos-latest
+          - windows-latest
     runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v3
@@ -24,8 +25,15 @@ jobs:
       with:
         python-version: ${{ matrix.python-version }}
         cache: "pip"
-    - name: Install Project
+    - name: Install Project (Windows)
+      if: runner.os == 'Windows'
+      run: make SHELL='C:/Program Files/Git/usr/bin/bash' install
+    - name: Install Project (Unix)
+      if: runner.os != 'Windows'
       run: make install
-
-    - name: Run Tests
+    - name: Run Tests (Windows)
+      if: runner.os == 'Windows'
+      run: make SHELL='C:/Program Files/Git/usr/bin/bash' test
+    - name: Run Tests (Unix)
+      if: runner.os != 'Windows'
       run: make test

Makefile

@@ -174,7 +174,7 @@ FORMAT_TARGETS?=
 export PATH:=$(if $(EXTRA_PATH),$(EXTRA_PATH):,)$(PATH)
 
 # Defensive settings for make: https://tech.davis-hansson.com/p/make/
-SHELL:=bash
+SHELL?=bash
 .ONESHELL:
 # for Makefile debugging purposes add -x to the .SHELLFLAGS
 .SHELLFLAGS:=-eu -o pipefail -O inherit_errexit -c