sample4_unittest.cc wrong comment? "Have side effect" or "not have side effect"?

[chjfth]

In current sample4_unittest.cc ,

googletest/googletest/samples/sample4_unittest.cc

Line 43 in 2d4f208

// EXPECT_EQ() evaluates its arguments exactly once, so they

The code is simiple:

TEST(Counter, Increment) {
  Counter c;

  // Test that counter 0 returns 0
  EXPECT_EQ(0, c.Decrement());

  // EXPECT_EQ() evaluates its arguments exactly once, so they
  // can have side effects.

  EXPECT_EQ(0, c.Increment());
  EXPECT_EQ(1, c.Increment());
  EXPECT_EQ(2, c.Increment());

  EXPECT_EQ(3, c.Decrement());
}

But I doubt the comment word is wrong. Since EXPECT_EQ is exactly once, EXPECT_EQ should have NO side effect, right?