Add chr() test snippets

tests/snippets/builtin_chr.py

@@ -0,0 +1,8 @@
+from testutils import assert_raises
+
+assert "a" == chr(97)
+assert "é" == chr(233)
+assert "🤡" == chr(129313)
+
+assert_raises(TypeError, lambda: chr(), "chr() takes exactly one argument (0 given)")
+assert_raises(ValueError, lambda: chr(0x110005), "ValueError: chr() arg not in range(0x110000)")