diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 3a8b40d..503c82e 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -4,24 +4,30 @@ on: [push]
 
 jobs:
   build:
-    env:
-      CMAKE_VERSION: 3.14.7
-    runs-on: ubuntu-18.04
+    runs-on: ${{ matrix.os }}
     strategy:
       matrix:
         python: [3.6, 3.7, 3.8]
+        os: [ubuntu-18.04, windows-latest]
     steps:
       - uses: actions/checkout@v1
       - name: Set up Python ${{ matrix.python }}
         uses: actions/setup-python@v1
         with:
           python-version: ${{ matrix.python }}
+      - name: Setup VC
+        uses: ilammy/msvc-dev-cmd@v1
+        if: contains(matrix.os, 'windows')
+      - name: Install CMake
+        if: contains(matrix.os, 'ubuntu')
+        run: |
+          CMAKE_VERSION=3.14.7
+          curl -sSL https://github.com/Kitware/CMake/releases/download/v$CMAKE_VERSION/cmake-$CMAKE_VERSION-Linux-x86_64.tar.gz | tar xz
+          sudo cp -rT cmake-$CMAKE_VERSION-Linux-x86_64 /usr/local
       - name: Install dependencies
         run: |
-          curl -sSL https://github.com/Kitware/CMake/releases/download/v$CMAKE_VERSION/cmake-$CMAKE_VERSION-Linux-x86_64.tar.gz | tar xz
           python -m pip install --upgrade setuptools pip wheel
           python -m pip install poetry tox-gh-actions
       - name: Test with tox
         run: |
-          export PATH=$GITHUB_WORKSPACE/cmake-$CMAKE_VERSION-Linux-x86_64/bin:$PATH
           tox
diff --git a/src/cmake_language_server/api.py b/src/cmake_language_server/api.py
index 0c9ed7c..488b6e8 100644
--- a/src/cmake_language_server/api.py
+++ b/src/cmake_language_server/api.py
@@ -48,7 +48,7 @@ class API(object):
   ]
 }''')
 
-        proc = subprocess.run([self._cmake, self._build],
+        proc = subprocess.run([self._cmake, str(self._build)],
                               universal_newlines=True,
                               stdout=subprocess.PIPE,
                               stderr=subprocess.PIPE)
@@ -131,11 +131,12 @@ foreach (variable ${variables})
   message("${variable}=${${variable}}")
 endforeach()
 ''')
-            p = subprocess.run([self._cmake, '-P', tmplist],
-                               cwd=cmake_files['paths']['source'],
-                               universal_newlines=True,
-                               stdout=subprocess.PIPE,
-                               stderr=subprocess.PIPE)
+            p = subprocess.run(
+                [self._cmake, '-P', str(tmplist)],
+                cwd=cmake_files['paths']['source'],
+                universal_newlines=True,
+                stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE)
             if p.returncode != 0:
                 return
 
diff --git a/tests/conftest.py b/tests/conftest.py
index 598524d..89fbfb1 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -7,10 +7,16 @@ def cmake_build(shared_datadir):
     source = shared_datadir / 'cmake'
     build = source / 'build'
     build.mkdir()
-    run(['cmake', source],
-        check=True,
-        cwd=build,
-        stdout=PIPE,
-        stderr=PIPE,
-        universal_newlines=True)
+    p = run(['cmake', str(source)],
+            cwd=build,
+            stdout=PIPE,
+            stderr=PIPE,
+            universal_newlines=True)
+    if p.returncode != 0:
+        import logging
+        import os
+        logging.error(os.environ)
+        logging.error(p.stdout)
+        logging.error(p.stderr)
+        raise RuntimeError("CMake failed")
     yield build
diff --git a/tests/test_api.py b/tests/test_api.py
index 44dadf1..e2baa04 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -35,7 +35,14 @@ def test_read_cmake_files(cmake_build):
     assert api.query()
     api.read_reply()
 
-    assert 'GNU' in api.get_variable_doc('CMAKE_CXX_COMPILER_ID')
+    import platform
+    system = platform.system()
+    if system == 'Linux':
+        assert 'GNU' in api.get_variable_doc('CMAKE_CXX_COMPILER_ID')
+    elif system == 'Windows':
+        assert 'MSVC' in api.get_variable_doc('CMAKE_CXX_COMPILER_ID')
+    else:
+        raise RuntimeError('Unexpected system')
 
 
 def test_parse_commands(cmake_build):
diff --git a/tox.ini b/tox.ini
index 7c68660..bbfb4a7 100644
--- a/tox.ini
+++ b/tox.ini
@@ -12,6 +12,7 @@ python =
 [testenv]
 whitelist_externals = poetry
 skip_install = true
+passenv = INCLUDE LIB LIBPATH
 commands_pre =
     poetry install
 commands =
@@ -23,5 +24,5 @@ skip_install = true
 commands =
     poetry run isort -c -rc src tests
     poetry run yapf -d -r src tests
-    poetry run flake8
+    poetry run flake8 src tests
     poetry run mypy src tests