add gherkin for SCP sequencer

gherkin/scp/sequencer.feature

@@ -0,0 +1,87 @@
+Feature: Sequencer
+  Once a StartInstance message is received, the sequencer filter its own transactions, sets a timer,
+  and begins simulating with a mailbox tracer.
+  It exchange messages with other sequencers and,
+  once the simulation produces a result, it votes and waits for a decision.
+
+  Background:
+    Given there is a chain "1" with sequencer "A"
+    Given there is a chain "2" with sequencer "B"
+
+  Scenario: Transaction filtering and timer
+    When sequencer "A" receives StartInstance with instance ID "0x1", period ID "1", sequence number "1", and xtrequest "1: [tx1_1,tx1_2], 2: [tx2]"
+    Then sequencer "A" should filter the transactions "[tx1_1,tx1_2]"
+    And sequencer "A" should start a timer for the instance "0x1"
+
+  Scenario: No transaction raises error
+    When sequencer "A" receives StartInstance with instance ID "0x1", period ID "1", sequence number "1", and xtrequest "2: [tx2], 3: [tx3]"
+    Then error "No transactions for this chain" should be returned
+
+  Scenario: Simulation raises error different from read miss
+    Given sequencer "A" receives StartInstance with instance ID "0x1", period ID "2", sequence number "2", and xtrequest "1: [tx1], 2: [tx2]"
+    When the execution engine simulates "tx1" and returns an error different than "Read miss"
+    Then sequencer "A" should send Vote to the shared publisher with instance ID "0x1", chain ID "1", and vote "false"
+
+  Scenario: Simulation successful
+    Given sequencer "A" receives StartInstance with instance ID "0x1", period ID "2", sequence number "2", and xtrequest "1: [tx1], 2: [tx2]"
+    When the execution engine simulates "tx1" and returns success
+    Then sequencer "A" should send Vote to the shared publisher with instance ID "0x1", chain ID "1", and vote "true"
+
+  Scenario: Read miss handled by storing expected message
+    Given sequencer "A" receives StartInstance with instance ID "0x1", period ID "2", sequence number "2", and xtrequest "1: [tx1], 2: [tx2]"
+    When the execution engine simulates "tx1" and returns a read miss for message with source chain ID "2", destination chain ID "1", sender "0xabc", receiver "0xdef", session ID "0x123", label "MSG", and data "data"
+    Then sequencer "A" store mailbox message with source chain ID "2", destination chain ID "1", sender "0xabc", receiver "0xdef", session ID "0x123", label "MSG", and data "data" as expected message for instance ID "0x1"
+
+  Scenario: Written message is sent to the destination sequencer
+    Given sequencer "A" receives StartInstance with instance ID "0x1", period ID "3", sequence number "9", and xtrequest "1: [tx1], 2: [tx2]"
+    When the execution engine simulates "tx1" and emits a MailboxMessage with source chain "1", destination chain "2", source "0xaaa", receiver "0xbbb", session ID "0x777", label "TRANSFER", and data "[0x01,0x02]"
+    Then sequencer "A" should send MailboxMessage to sequencer "B" with instance ID "0x1", source chain "1", destination chain "2", source "0xaaa", receiver "0xbbb", session ID "0x777", label "TRANSFER", and data "[0x01,0x02]"
+
+  Scenario: A received mailbox message is stored as pending
+    Given sequencer "A" receives StartInstance with instance ID "0x1", period ID "3", sequence number "9", and xtrequest "1: [tx1], 2: [tx2]"
+    When sequencer "A" receives MailboxMessage with instance ID "0x1", source chain "2", destination chain "1", source "0x222", receiver "0x111", session ID "0x999", label "NOTE", and data "[0xab]"
+    Then sequencer "A" should append to the pending mailbox queue for instance ID "0x1" the message with source chain "2", destination chain "1", source "0x222", receiver "0x111", session ID "0x999", label "NOTE", and data "[0xab]"
+    And sequencer "A" should not trigger a new simulation
+
+  Scenario: A received mailbox message that is expected is added to the inbox and triggers a new simulation
+    Given sequencer "A" receives StartInstance with instance ID "0x1", period ID "2", sequence number "2", and xtrequest "1: [tx1], 2: [tx2]"
+    And the execution engine simulates "tx1" and returns a read miss for message with source chain ID "2", destination chain ID "1", sender "0xabc", receiver "0xdef", session ID "0x123", label "MSG", and data "data"
+    And sequencer "A" store mailbox message with source chain ID "2", destination chain ID "1", sender "0xabc", receiver "0xdef", session ID "0x123", label "MSG", and data "data" as expected message for instance ID "0x1"
+    When sequencer "A" receives MailboxMessage with instance ID "0x1", source chain "2", destination chain "1", source "0xabc", receiver "0xdef", session ID "0x123", label "MSG", and data "data"
+    Then the sequencer should insert a mailbox.putInbox transaction above the transaction list for the message with source chain "2", destination chain "1", source "0xabc", receiver "0xdef", session ID "0x123", label "MSG", and data "data"
+    And sequencer "A" should start a new simulation
+
+  Scenario: Timeout before voting causes a rejection
+    Given sequencer "A" receives StartInstance with instance ID "0x1", period ID "2", sequence number "2", and xtrequest "1: [tx1], 2: [tx2]"
+    When the timer for instance ID "0x1" expires
+    Then sequencer "A" should send Vote to the shared publisher with instance ID "0x1", chain ID "1", and vote "false"
+    And sequencer "A" should mark the instance as rejected
+
+  Scenario: Timeout after voting causes no action
+    Given sequencer "A" receives StartInstance with instance ID "0x1", period ID "2", sequence number "2", and xtrequest "1: [tx1], 2: [tx2]"
+    And sequencer "A" sent Vote to the shared publisher with instance ID "0x1", chain ID "1", and vote "_"
+    When the timer for instance ID "0x1" expires
+    Then no additional Vote message should be sent
+
+  Scenario: Decision false causes rejection
+    Given sequencer "A" receives StartInstance with instance ID "0x1", period ID "2", sequence number "2", and xtrequest "1: [tx1], 2: [tx2]"
+    When sequencer "A" receives Decided from the shared publisher with instance ID "0x1" and decision "false"
+    Then sequencer "A" should mark the instance as rejected
+
+  Scenario: If decision true is received but no vote was sent, an error is raised
+    Given sequencer "A" receives StartInstance with instance ID "0x1", period ID "2", sequence number "2", and xtrequest "1: [tx1], 2: [tx2]"
+    When sequencer "A" receives Decided from the shared publisher with instance ID "0x1" and decision "true"
+    Then error "decision true but no vote sent is an impossible state" should be returned
+
+  Scenario: Decision true causes finalization
+    Given sequencer "A" receives StartInstance with instance ID "0x1", period ID "2", sequence number "2", and xtrequest "1: [tx1], 2: [tx2]"
+    And the execution engine simulates "tx1" and returns success
+    And sequencer "A" sent Vote to the shared publisher with instance ID "0x1", chain ID "1", and vote "true"
+    When sequencer "A" receives Decided from the shared publisher with instance ID "0x1" and decision "true"
+    Then sequencer "A" should accept the instance
+
+  Scenario: Double decided is ignored and error is raised
+    Given sequencer "A" receives StartInstance with instance ID "0x1", period ID "2", sequence number "2", and xtrequest "1: [tx1], 2: [tx2]"
+    And sequencer "A" receives Decided from the shared publisher with instance ID "0x1" and decision "false"
+    When sequencer "A" receives Decided from the shared publisher with instance ID "0x1" and decision "true"
+    Then error "instance already decided" should be returned