[3.15] gh-149219: Test frozendict in Lib/test/test_crossinterp.py (GH-149220) (#150186)

gh-149219: Test `frozendict` in `Lib/test/test_crossinterp.py` (GH-149220)
(cherry picked from commit c35b0f2)

Co-authored-by: sobolevn <mail@sobolevn.me>

Author: miss-islington

Lib/test/test_crossinterp.py

@@ -157,6 +157,10 @@ def ignore_byteswarning():
     {},
     {1: 7, 2: 8, 3: 9},
     {1: [1], 2: (2,), 3: {3: 4}},
+    # frozendict
+    frozendict(),
+    frozendict({1: 7, 2: 8, 3: 9}),
+    frozendict({1: [1], 2: (2,), 3: {3: 4}, 4: frozendict({5: 6})}),
     # set
     set(),
     {1, 2, 3},