1 files changed, 39 insertions, 0 deletions
diff --git a/tests/test_builder.py b/tests/test_builder.py
new file mode 100644
index 0000000..1ff8aea
--- /dev/null
+++ b/tests/test_builder.py
@@ -0,0 +1,39 @@
+"""Test the Builder class."""
+import pytest
+
+
+@pytest.mark.sphinx('dummy', srcdir="test_builder", freshenv=True)
+def test_incremental_reading(app):
+    # first reading
+    updated = app.builder.read()
+    assert set(updated) == app.env.found_docs == set(app.env.all_docs)
+    assert updated == sorted(updated)  # sorted by alphanumeric
+
+    # test if exclude_patterns works ok
+    assert 'subdir/excluded' not in app.env.found_docs
+
+    # before second reading, add, modify and remove source files
+    (app.srcdir / 'new.txt').write_text('New file\n========\n', encoding='utf8')
+    app.env.all_docs['index'] = 0  # mark as modified
+    (app.srcdir / 'autodoc.txt').unlink()
+
+    # second reading
+    updated = app.builder.read()
+
+    assert set(updated) == {'index', 'new'}
+    assert 'autodoc' not in app.env.all_docs
+    assert 'autodoc' not in app.env.found_docs
+
+
+@pytest.mark.sphinx('dummy', testroot='warnings', freshenv=True)
+def test_incremental_reading_for_missing_files(app):
+    # first reading
+    updated = app.builder.read()
+    assert set(updated) == app.env.found_docs == set(app.env.all_docs)
+
+    # second reading
+    updated = app.builder.read()
+
+    # "index" is listed up to updated because it contains references
+    # to nonexisting downloadable or image files
+    assert set(updated) == {'index'}