Simple run_pymodules_install test, refs #1898

Regression test for the fix introduced in #1898.

tests/test_build.py

@@ -0,0 +1,23 @@
+try:
+    from unittest import mock
+except ImportError:
+    # `Python 2` or lower than `Python 3.3` does not
+    # have the `unittest.mock` module built-in
+    import mock
+from pythonforandroid.build import run_pymodules_install
+
+
+class TestBuildBasic:
+
+    def test_run_pymodules_install_optional_project_dir(self):
+        """
+        Makes sure the `run_pymodules_install()` doesn't crash when the
+        `project_dir` optional parameter is None, refs #1898
+        """
+        ctx = mock.Mock()
+        modules = []
+        project_dir = None
+        with mock.patch('pythonforandroid.build.info') as m_info:
+            assert run_pymodules_install(ctx, modules, project_dir) is None
+        assert m_info.call_args_list[-1] == mock.call(
+            'No Python modules and no setup.py to process, skipping')