Thanks to everybody's suggestions.
I fixed it this way:

I removed TEST_NODE2 as a failover member
I removed TEST_NODE1 mirror configuration
I stopped IRIS on TEST_NODE2 & TEST_NODE1
I removed all the journals as DB files IRIS.DAT are identical
I started IRIS on  TEST_NODE1 then  TEST_NODE2 
I configured the mirror on TEST_NODE1
I configured TEST_NODE2 as a failover member
Now Mirror Monitor in SMP[System Management Portal] GUI is showing no errors