Test only 1 project example per dev/platform for AppVeyor CI

.appveyor.yml

@@ -11,8 +11,6 @@ environment:
 install:
   - cmd: git submodule update --init --recursive
   - cmd: SET PATH=C:\MinGW\bin;%PATH%
-  - if %PLATFORM% == x64 SET PATH=C:\Python27-x64;C:\Python27-x64\Scripts;%PATH%
-  - if %PLATFORM% == x86 SET PATH=C:\Python27;C:\Python27\Scripts;%PATH%
   - cmd: pip install tox
 
 test_script:

tests/test_examples.py

@@ -14,7 +14,7 @@
 
 import random
 from glob import glob
-from os import listdir, walk
+from os import getenv, listdir, walk
 from os.path import dirname, getsize, isdir, isfile, join, normpath
 
 import pytest
@@ -54,11 +54,16 @@ def pytest_generate_tests(metafunc):
                 continue
             platform_examples.append(root)
 
-        # test random 3 examples
         random.shuffle(platform_examples)
-        project_dirs.extend(platform_examples[:3])
-    project_dirs.sort()
-    metafunc.parametrize("pioproject_dir", project_dirs)
+
+        if getenv("APPVEYOR"):
+            # use only 1 example for AppVeyor CI
+            project_dirs.append(platform_examples[0])
+        else:
+            # test random 3 examples
+            project_dirs.extend(platform_examples[:3])
+
+    metafunc.parametrize("pioproject_dir", sorted(project_dirs))
 
 
 @pytest.mark.examples