Add test for brackets within f-string.

Author: domdfcoding

tests/test_fstring_brackets.py

@@ -0,0 +1,15 @@
+# this package
+from formate_trailing_commas import trailing_commas_hook
+
+
+def test_problem_code():
+	src = """
+print(
+		"Average build time:",
+		f"{statistics.mean(build_times)}s,",
+		f"σ {statistics.stdev(build_times)}",
+		f"(n={len(build_times)})",
+)
+"""
+
+	assert trailing_commas_hook(src) == src