You will need two browsers open, and logged in as two different users, U1 and U2. You will also need a third user, U3 U1: Add U2 and U3 as a messaging contacts. U2: Send a message to U1 U1: Logout U1: Login U1: Verify that you get a popup notification for the message, click through and read it. U1: Click to change to the message stream for U3. U2: Send a message to U1 U1: While still viewing U3's messages, click the block icon next to U2 U1: Logout U1: Login U1: You should not see a popup notification. In the database, look at the last record in mdl_message_read, confirm that it is the message that you sent, and that the message has content in 'fullmessage' and that timecreated appears proper (not 0)