The behavior of this implementation was changed slightly with the switch to EXTCODEHASH. Let's document this using test cases.

Mocks:

• Contract R
  • Has a token receive function which emits an event Received
• Contract A is R
  • Has constructor
    1. Deploys NFToken
    2. Mints token id=1
    3. Transfers token id=1 to self
• Contract B
  • Has constructor
    1. Deploys NFToken
    2. Deploys R
    3. Transfers token id=1 to R

Tests:

1. Test 1
   1. Transaction 1 -- Deploy NFToken
   2. Transaction 2 -- Mint token id=1
   3. Transaction 3 -- Deploy Contract R
   4. Transaction 4 -- Transfer token id=1 to R
   5. Expect NO event on Constantinople
2. Test 2
   1. Transaction 1 -- Deploy NFToken
   2. Transaction 2 -- Mint token id=1
   3. Transaction 3 -- Deploy Contract R
   4. Expect NO event on Constantinople
3. Test 3
   1. Transaction 1 -- Deploy Contract B
   2. Expect event on Constantinople (but no event with same test using old version of implementation)