1 files changed, 34 insertions, 0 deletions
diff --git a/toolkit/components/glean/tests/pytest/expect_helper.py b/toolkit/components/glean/tests/pytest/expect_helper.py
new file mode 100644
index 0000000000..543ef04026
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/expect_helper.py
@@ -0,0 +1,34 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import inspect
+import os
+
+
+def expect(path, actual):
+    """
+    Assert that the content of the file at `path` contains `actual`.
+
+    If the environment variable `UPDATE_EXPECT` is set, the path content is updated to `actual`.
+    This allows to update the file contents easily.
+    """
+
+    callerframerecord = inspect.stack()[1]
+    frame = callerframerecord[0]
+    info = inspect.getframeinfo(frame)
+    msg = f"""
+Unexpected content in {path} (at {info.filename}:{info.lineno})
+
+If the code generation was changed,
+run the test suite again with `UPDATE_EXPECT=1` set to update the test files.
+""".strip()
+
+    if "UPDATE_EXPECT" in os.environ:
+        with open(path, "w") as file:
+            file.write(actual)
+
+    expected = None
+    with open(path, "r") as file:
+        expected = file.read()
+    assert actual == expected, msg