Add testcase for specific build

tests/test_application.py

@@ -7,6 +7,9 @@
     :copyright: Copyright 2007-2019 by the Sphinx team, see AUTHORS.
     :license: BSD, see LICENSE for details.
 """
+
+from unittest.mock import Mock
+
 import pytest
 from docutils import nodes
 
@@ -113,3 +116,22 @@ def test_add_is_parallel_allowed(app, status, warning):
             "for parallel reading, assuming it isn't - please ") in warning.getvalue()
     app.extensions.pop('write_serial')
     warning.truncate(0)  # reset warnings
+
+
+@pytest.mark.sphinx('dummy', testroot='root')
+def test_build_specific(app):
+    app.builder.build = Mock()
+    filenames = [app.srcdir / 'index.txt',                      # normal
+                 app.srcdir / 'images',                         # without suffix
+                 app.srcdir / 'notfound.txt',                   # not found
+                 app.srcdir / 'img.png',                        # unknown suffix
+                 '/index.txt',                                  # external file
+                 app.srcdir / 'subdir',                         # directory
+                 app.srcdir / 'subdir/includes.txt',            # file on subdir
+                 app.srcdir / 'subdir/../subdir/excluded.txt']  # not normalized
+    app.build(False, filenames)
+
+    expected = ['index', 'images', 'img.png', 'subdir/includes', 'subdir/excluded']
+    app.builder.build.assert_called_with(expected,
+                                         method='specific',
+                                         summary='5 source files given on command line')