TEST(PermutationTest, Inverse) {
  Permutation p = Permutation(create_image(3, 1, 2, 0));

  Permutation inverse = p.inverse();

  EXPECT_EQ(2, inverse(0));
  EXPECT_EQ(0, inverse(1));
  EXPECT_EQ(1, inverse(2));
}
TEST(PermutationTest, Inequality) {
  Permutation p = Permutation(create_image(3, 1, 2, 0)).inverse();

  EXPECT_NE(p, p.inverse());
}