diff --git a/.circleci/config.yml b/.circleci/config.yml
index 810608fa..17f13e49 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -10,7 +10,7 @@ version: 2
     - run:
         name: Run the tests in a container
         command: |
-          docker run --rm -v `pwd`:`pwd` -w `pwd` "pqclean/ci-container:$ARCH" /bin/bash -c "
+          docker run -e CI=true --rm -v `pwd`:`pwd` -w `pwd` "pqclean/ci-container:$ARCH" /bin/bash -c "
           uname -a &&
           export CC=${CC} &&
           cd test && python3 -m nose --rednose --verbose"
diff --git a/appveyor.yml b/appveyor.yml
index 41bc098f..956ad13d 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -12,14 +12,16 @@ environment:
 
 init:
   - call "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars%BITS%.bat"
-  - set PATH="C:\\Python37";"C:\\Python37\Scripts";"C:\\tmp\\tools";%PATH%
-  - mkdir "C:\tmp\tools"
     # Download AStyle 3.1: first enable strong crypto in Invoke-WebRequest
   - ps: Set-ItemProperty -Path "HKLM:\SOFTWARE\Wow6432Node\Microsoft\.NetFramework\v4.0.30319" -Name 'SchUseStrongCrypto' -Value '1' -Type DWord
   - ps: Set-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\.NetFramework\v4.0.30319" -Name "SchUseStrongCrypto" -Value '1' -Type DWord
-  - ps: Invoke-WebRequest -OutFile "C:\tmp\tools\AStyle.exe" "https://rded.nl/pqclean/AStyle.exe"
+    # Add Python to PATH
+  - set PATH="C:\\Python37";"C:\\Python37\Scripts";%PATH%
 
 build_script:
   - python -m pip install -r requirements.txt
   - cd test
+    # Download Astyle to local folder because putting it in PATH doesn't work
+  - ps: Invoke-WebRequest -OutFile "astyle.exe" "https://rded.nl/pqclean/AStyle.exe"
+    # Run tests
   - python -m nose -v --rednose
diff --git a/test/Makefile.Microsoft_nmake b/test/Makefile.Microsoft_nmake
index e0e057fb..21afb364 100644
--- a/test/Makefile.Microsoft_nmake
+++ b/test/Makefile.Microsoft_nmake
@@ -39,7 +39,7 @@ $(DEST_DIR)\functest_$(SCHEME)_$(IMPLEMENTATION).exe: build-scheme $(COMMON_OBJE
     -MKDIR $(DEST_DIR)
     -DEL functest.obj
     $(CC) /c crypto_$(TYPE)\functest.c $(CFLAGS) /I $(SCHEME_DIR) /DPQCLEAN_NAMESPACE=PQCLEAN_$(SCHEME_UPPERCASE)_$(IMPLEMENTATION_UPPERCASE)
-    LINK.EXE /OUT:$@ functest.obj $(COMMON_OBJECTS_NOPATH) notrandombytes.obj $(SCHEME_DIR)\lib$(SCHEME)_$(IMPLEMENTATION).lib Advapi32.lib
+    LINK.EXE /OUT:$@ functest.obj $(COMMON_OBJECTS_NOPATH) randombytes.obj $(SCHEME_DIR)\lib$(SCHEME)_$(IMPLEMENTATION).lib Advapi32.lib
 
 $(DEST_DIR)\testvectors_$(SCHEME)_$(IMPLEMENTATION).exe: build-scheme $(COMMON_OBJECTS) $(COMMON_DIR)\notrandombytes.obj
     -MKDIR $(DEST_DIR)
diff --git a/test/helpers.py b/test/helpers.py
index 0f043691..238e234c 100644
--- a/test/helpers.py
+++ b/test/helpers.py
@@ -2,6 +2,8 @@ import functools
 import os
 import subprocess
 import unittest
+import shutil
+import sys
 
 
 def run_subprocess(command, working_dir='.', env=None, expected_returncode=0):
@@ -44,7 +46,8 @@ def make(*args, working_dir='.', env=None, expected_returncode=0, **kwargs):
         # we need SCHEME_UPPERCASE and IMPLEMENTATION_UPPERCASE with nmake
         for envvar in ['IMPLEMENTATION', 'SCHEME']:
             if envvar in kwargs:
-                kwargs['{}_UPPERCASE'.format(envvar)] = kwargs[envvar].upper().replace('-', '')
+                kwargs['{}_UPPERCASE'.format(envvar)] = (
+                        kwargs[envvar].upper().replace('-', ''))
     else:
         make_command = ['make']
 
@@ -69,4 +72,29 @@ def skip_windows(message="This test is not supported on Windows"):
             return skip_windows
         else:
             return f
-    return wrapper
\ No newline at end of file
+    return wrapper
+
+
+def ensure_available(executable):
+    """
+    Checks if a command is available.
+
+    If a command MUST be available, because we are in a CI environment,
+    raises an AssertionError.
+
+    In the docker containers, on Travis and on Windows, CI=true is set.
+    """
+    path = shutil.which(executable)
+    if path:
+        print("Found", path)
+        return path
+
+    # Installing clang-tidy on LLVM will be too much of a mess.
+    if ((executable == 'clang-tidy' and sys.platform == 'darwin')
+            or 'CI' not in os.environ):
+        raise unittest.SkipTest(
+                "{} is not available on PATH. Install it to run this test.{}"
+                .format(executable, "" if not os.name == 'nt'
+                        else "On Windows, make sure to add it to PATH")
+                )
+    raise AssertionError("{} not available on CI".format(executable))
diff --git a/test/test_format.py b/test/test_format.py
index e94e3deb..09cc61fd 100644
--- a/test/test_format.py
+++ b/test/test_format.py
@@ -1,8 +1,5 @@
-import shutil
-import unittest
-
 import pqclean
-from helpers import run_subprocess
+from helpers import run_subprocess, ensure_available
 
 
 def test_formatting():
@@ -12,8 +9,7 @@ def test_formatting():
 
 
 def check_format(implementation: pqclean.Implementation):
-    if shutil.which('astyle') is None:
-        raise unittest.SkipTest("AStyle is not installed")
+    ensure_available('astyle')
     cfiles = implementation.cfiles()
     hfiles = implementation.hfiles()
     run_subprocess(['astyle',
diff --git a/test/test_functest.py b/test/test_functest.py
index 465b639a..01807e75 100644
--- a/test/test_functest.py
+++ b/test/test_functest.py
@@ -24,7 +24,7 @@ def test_functest_sanitizers():
 
 
 def check_functest(implementation):
-    helpers.make(#'functest',
+    helpers.make('functest',
                  TYPE=implementation.scheme.type,
                  SCHEME=implementation.scheme.name,
                  IMPLEMENTATION=implementation.name,
@@ -48,6 +48,8 @@ def check_functest_sanitizers(implementation):
         env = {'ASAN_OPTIONS': 'detect_leaks=0'}
     else:
         print("Supported platform: {}".format(platform.machine()))
+
+    helpers.ensure_available('valgrind')
     helpers.make('clean-scheme', 'functest',
                  TYPE=implementation.scheme.type,
                  SCHEME=implementation.scheme.name,
diff --git a/test/test_linter.py b/test/test_linter.py
index 8d6b6839..33563f8b 100644
--- a/test/test_linter.py
+++ b/test/test_linter.py
@@ -1,10 +1,8 @@
 import os
 from glob import glob
-import shutil
-import unittest
 
 import pqclean
-from helpers import run_subprocess
+from helpers import run_subprocess, ensure_available
 
 
 def test_clang_tidy():
@@ -14,8 +12,7 @@ def test_clang_tidy():
 
 
 def check_tidy(implementation: pqclean.Implementation):
-    if shutil.which('clang-tidy') is None:
-        raise unittest.SkipTest("clang-tidy unavailable in PATH")
+    ensure_available('clang-tidy')
     cfiles = glob(os.path.join(implementation.path(), '*.c'))
     common_files = glob(os.path.join('..', 'common', '*.c'))
     run_subprocess(['clang-tidy',