diff --git a/.gitignore b/.gitignore
index 2d57dbb..abbc1af 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,7 @@
 
 # Binaries
 bin
+solcx/temp
 
 # C extensions
 *.so
@@ -58,3 +59,6 @@ docs/_build
 
 # npm
 node_modules
+
+# other
+.vscode
diff --git a/.travis.yml b/.travis.yml
index 36e93cd..6281ccd 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,189 +1,40 @@
-language: python
-python:
-  - "3.5"
-os:
-  - linux
-dist: trusty
-sudo: required
-env:
-  global:
-    - SOLC_BASE_INSTALL_PATH=$TRAVIS_BUILD_DIR
+# Based on https://github.com/cclauss/Travis-CI-Python-on-three-OSes
 matrix:
   include:
-    # lint
-    - python: "3.5"
-      env: TOX_POSARGS="-e flake8"
-    # installation
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34-installation"
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35-installation"
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36-installation"
-    # solc 0.4.1
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.1
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.1
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.1
-    # solc 0.4.2
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.2
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.2
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.2
-    # solc 0.4.6
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.6
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.6
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.6
-    # solc 0.4.7
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.7
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.7
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.7
-    # solc 0.4.8
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.8
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.8
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.8
-    # solc 0.4.9
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.9
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.9
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.9
-    # solc 0.4.11
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.11
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.11
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.11
-    # solc 0.4.12
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.12
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.12
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.12
-    # solc 0.4.13
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.13
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.13
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.13
-    # solc 0.4.14
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.14
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.14
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.14
-    # solc 0.4.15
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.15
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.15
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.15
-    # solc 0.4.16
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.16
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.16
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.16
-    # solc 0.4.17
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.17
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.17
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.17
-    # solc 0.4.18
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.18
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.18
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.18
-    # solc 0.4.19
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.19
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.19
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.19
-    # solc 0.4.20
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.20
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.20
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.20
-    # solc 0.4.21
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.21
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.21
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.21
-    # solc 0.4.22
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.22
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.22
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.22
-    # solc 0.4.23
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.23
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.23
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.23
-    # solc 0.4.24
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.24
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.24
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.24
-    # solc 0.4.25
-    - python: "3.4"
-      env: TOX_POSARGS="-e py34" SOLC_VERSION=v0.4.25
-    - python: "3.5"
-      env: TOX_POSARGS="-e py35" SOLC_VERSION=v0.4.25
-    - python: "3.6"
-      env: TOX_POSARGS="-e py36" SOLC_VERSION=v0.4.25
+    - name: "Python 3.7.1 on Xenial Linux"
+      language: python  
+      python: 3.7           # this works for Linux but is ignored on macOS or Windows
+      dist: xenial          # required for Python >= 3.7
+      sudo: true
+      install:
+        - sudo add-apt-repository -y ppa:ethereum/ethereum
+        - sudo apt-get update
+        - sudo apt-get install -y solc
+        - pip install -r requirements-dev.txt
+        - pip install flake8
+      script: flake8 solcx/ tests/ --max-line-length=100
+    - name: "Python 3.6.8 on Xenial Linux"
+      language: python
+      python: 3.6
+      dist: xenial
+      sudo: true
+      install:
+        - sudo add-apt-repository -y ppa:ethereum/ethereum
+        - sudo apt-get update
+        - sudo apt-get install -y solc
+        - pip install -r requirements-dev.txt
+      script: python -m pytest tests/ --cov=solcx/
+    - name: "Python 3.7.3 on Windows"
+      os: windows           # Windows 10.0.17134 N/A Build 17134
+      language: shell       # 'language: python' is an error on Travis CI Windows
+      # python: 3.7         # 'python:' is ignored on Travis CI Windows
+      install:
+        - choco install python  # this install takes at least 1 min 30 sec
+        - python -m pip install --upgrade pip
+        - pip3 install -r requirements-dev.txt
+      env: PATH=/c/Python37:/c/Python37/Scripts:$PATH
 
-cache:
-  - pip: true
-before_install:
-install:
-  - travis_retry pip install setuptools --upgrade
-  - travis_retry pip install tox
-  - pip --version
-  - pip install -e .  # install py-solc globally in order to use the solc installation scripts.
-before_script:
-  - python --version
-  - if [ -n "$SOLC_VERSION" ]; then python -m solc.install $SOLC_VERSION; fi
-  - if [ -n "$SOLC_VERSION" ]; then export SOLC_BINARY="$SOLC_BASE_INSTALL_PATH/solc-$SOLC_VERSION/bin/solc"; fi
-  - if [ -n "$SOLC_VERSION" ]; then export LD_LIBRARY_PATH="$SOLC_BASE_INSTALL_PATH/solc-$SOLC_VERSION/bin"; fi
-  - env
-  - if [ -n "$SOLC_BINARY" ]; then $SOLC_BINARY --version; fi
-script:
-  - tox $TOX_POSARGS
-after_script:
-  - cat .tox/$TOX_POSARGS/log/*.log
+script: python -m pytest tests --cov=solcx/
+after_success: coveralls
+notifications:
+  email: false
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 7c536b3..bdfaad9 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -1,5 +1,6 @@
-pytest>=2.9.2
-tox>=2.3.1
+coveralls==1.7.0
+pytest>=5.0.0
+pytest-cov>=2.7.1
 semantic_version>=2.6.0
-bumpversion==0.5.3
-twine==1.12.1
+twine==1.13.0
+requests>=2.19.0
\ No newline at end of file
diff --git a/solcx/install.py b/solcx/install.py
index 1272180..1f59a7d 100644
--- a/solcx/install.py
+++ b/solcx/install.py
@@ -142,10 +142,10 @@ def set_solc_version_pragma(version, silent=False):
         print("Using solc version {}".format(solc_version))
 
 
-def get_available_solc_versions():
+def get_available_solc_versions(headers={}):
     versions = []
     pattern = VERSION_REGEX[_get_platform()]
-    for release in requests.get(ALL_RELEASES).json():
+    for release in requests.get(ALL_RELEASES, headers=headers).json():
         asset = next((i for i in release['assets'] if re.match(pattern, i['name'])), False)
         if asset:
             versions.append(release['tag_name'])
diff --git a/solcx/temp/solc-binary b/solcx/temp/solc-binary
deleted file mode 100644
index 836a508..0000000
Binary files a/solcx/temp/solc-binary and /dev/null differ
diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..b9464d3
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,52 @@
+from base64 import b64encode
+import os
+import pytest
+import sys
+
+import solcx
+
+TEST_CONTRACT = '''pragma solidity >=0.4.11 <0.6.0;
+
+contract Foo {
+    function return13() public returns (uint) {
+        return 13;
+    }
+}
+'''
+
+if sys.platform == "darwin":
+    VERSIONS = solcx.get_installed_solc_versions()
+else:
+    auth = b64encode(os.environ['GITAUTH'].encode()).decode('ascii')
+    headers = {'Authorization': f"Basic {auth}"}
+    VERSIONS = solcx.get_available_solc_versions(headers=headers)
+
+
+def pytest_generate_tests(metafunc):
+    if 'all_versions' in metafunc.fixturenames:
+        metafunc.parametrize('all_versions', VERSIONS, indirect=True)
+
+
+_installed = {}
+@pytest.fixture()
+def all_versions(request):
+    version = request.param
+    if version not in _installed:
+        try:
+            solcx.install_solc(version)
+            _installed[version] = True
+        except Exception:
+            _installed[version] = False
+            pytest.fail(f"Unable to install solc {version}")
+    if _installed[version]:
+        solcx.set_solc_version(version)
+    else:
+        request.applymarker('skip')
+
+
+@pytest.fixture()
+def contract_source(tmp_path):
+    source = tmp_path.joinpath('test.sol')
+    with source.open('w') as fp:
+        fp.write(TEST_CONTRACT)
+    return str(source)
diff --git a/tests/test_compile.py b/tests/test_compile.py
new file mode 100644
index 0000000..4ff7f04
--- /dev/null
+++ b/tests/test_compile.py
@@ -0,0 +1,12 @@
+import pytest
+
+import solcx
+
+
+@pytest.fixture(autouse=True)
+def setup(all_versions):
+    pass
+
+
+def test_compile_files(contract_source):
+    solcx.compile_files([contract_source])
diff --git a/tox.ini b/tox.ini
deleted file mode 100644
index f758cae..0000000
--- a/tox.ini
+++ /dev/null
@@ -1,30 +0,0 @@
-[tox]
-envlist=
-    py{34,35,36}-{core,installation}
-    flake8
-
-[flake8]
-max-line-length= 100
-exclude= tests/*
-
-[testenv]
-commands=
-    core: py.test {posargs:tests/core}
-    installation: py.test {posargs:-s tests/installation}
-passenv =
-    SOLC_BINARY
-    TRAVIS_BUILD_DIR
-    SOLC_RUN_INSTALL_TESTS
-setenv =
-    py{34,35,36}-installation: SOLC_RUN_INSTALL_TESTS=enabled
-deps =
-    -r{toxinidir}/requirements-dev.txt
-basepython =
-    py34: python3.4
-    py35: python3.5
-    py36: python3.6
-
-[testenv:flake8]
-basepython=python
-deps=flake8
-commands=flake8 {toxinidir}/solc