allow some tests (except on CI) to be skipped when svn/hg are unavail…

…able (#182)

* FIX: Regression if subversion or mercurial are missing

Split-up test_validate() into two parts:
* test_validate: Part requires only git
* test_validate2: Part requires subversion (svn) and mercurial (hg)
* test_validate2 is skipped if either svn or hg are not installed
* support: FAKE-PROGRAM detection that exist (svn)
  but only states that the program is missing if it is run
  (usecase: macOS for svn that was a former part of Xcode).

* Disable skip-test functionality when CI environment variable is set.

NOTE: All tests should be executed when CI is used.

* refactor / cleanup

Co-authored-by: Dirk Thomas <dirk-thomas@users.noreply.github.com>

test/test_commands.py

@@ -1,4 +1,5 @@
 import os
+from shutil import which
 import subprocess
 import sys
 import unittest
@@ -15,6 +16,17 @@
 TEST_WORKSPACE = os.path.join(
     os.path.dirname(os.path.dirname(__file__)), 'test_workspace')
 
+CI = os.environ.get('CI') == 'true'  # Travis CI / Github actions set: CI=true
+svn = which('svn')
+hg = which('hg')
+if svn:
+    # check if the svn executable is usable (on macOS)
+    # and not only exists to state that the program is not installed
+    try:
+        subprocess.check_call([svn, '--version'])
+    except subprocess.CalledProcessError:
+        svn = False
+
 
 class TestCommands(unittest.TestCase):
 
@@ -292,13 +304,16 @@ def test_validate(self):
         self.assertEqual(output, expected)
 
         output = run_command(
-            'validate', ['--input', REPOS2_FILE])
-        expected = get_expected_output('validate2')
+            'validate', ['--hide-empty', '--input', REPOS_FILE])
+        expected = get_expected_output('validate_hide')
         self.assertEqual(output, expected)
 
+    @unittest.skipIf(not svn and not CI, '`svn` was not found')
+    @unittest.skipIf(not hg and not CI, '`hg` was not found')
+    def test_validate_svn_and_hg(self):
         output = run_command(
-            'validate', ['--hide-empty', '--input', REPOS_FILE])
-        expected = get_expected_output('validate_hide')
+            'validate', ['--input', REPOS2_FILE])
+        expected = get_expected_output('validate2')
         self.assertEqual(output, expected)
 
     def test_remote(self):