1 files changed, 62 insertions, 0 deletions
diff --git a/tests/utils/savefile.py b/tests/utils/savefile.py
new file mode 100644
index 000000000..87f9f4b0a
--- /dev/null
+++ b/tests/utils/savefile.py
@@ -0,0 +1,62 @@
+import os
+import pytest
+
+from buildstream.utils import save_file_atomic
+
+
+def test_save_new_file(tmpdir):
+    filename = os.path.join(tmpdir, 'savefile-success.test')
+    with save_file_atomic(filename, 'w') as f:
+        f.write('foo\n')
+
+    assert os.listdir(tmpdir) == ['savefile-success.test']
+    with open(filename) as f:
+        assert f.read() == 'foo\n'
+
+
+def test_save_over_existing_file(tmpdir):
+    filename = os.path.join(tmpdir, 'savefile-overwrite.test')
+
+    with open(filename, 'w') as f:
+        f.write('existing contents\n')
+
+    with save_file_atomic(filename, 'w') as f:
+        f.write('overwritten contents\n')
+
+    assert os.listdir(tmpdir) == ['savefile-overwrite.test']
+    with open(filename) as f:
+        assert f.read() == 'overwritten contents\n'
+
+
+def test_exception_new_file(tmpdir):
+    filename = os.path.join(tmpdir, 'savefile-exception.test')
+
+    with pytest.raises(RuntimeError):
+        with save_file_atomic(filename, 'w') as f:
+            f.write('Some junk\n')
+            raise RuntimeError("Something goes wrong")
+
+    assert os.listdir(tmpdir) == []
+
+
+def test_exception_existing_file(tmpdir):
+    filename = os.path.join(tmpdir, 'savefile-existing.test')
+
+    with open(filename, 'w') as f:
+        f.write('existing contents\n')
+
+    with pytest.raises(RuntimeError):
+        with save_file_atomic(filename, 'w') as f:
+            f.write('Some junk\n')
+            raise RuntimeError("Something goes wrong")
+
+    assert os.listdir(tmpdir) == ['savefile-existing.test']
+    with open(filename) as f:
+        assert f.read() == 'existing contents\n'
+
+
+def test_attributes(tmpdir):
+    filename = os.path.join(tmpdir, 'savefile-attributes.test')
+    with save_file_atomic(filename, 'w') as f:
+        assert f.real_filename == filename
+        assert f.name != filename