tests: Add extra tests to check the case when a rule return nil action (#2966)

Author: infrmtcs

consensus/tendermint/rule_proposal_and_polka_current_test.go

@@ -32,6 +32,43 @@ func TestProposalAndPolkaCurrent(t *testing.T) {
 		assertState(t, stateMachine, types.Height(0), types.Round(0), types.StepPrecommit)
 	})
 
+	t.Run("Line 36: lock and broadcast precommit when step is precommit", func(t *testing.T) {
+		stateMachine := setupStateMachine(t, 4, 3)
+		currentRound := newTestRound(t, stateMachine, 0, 0)
+		nextRound := newTestRound(t, stateMachine, 1, 0)
+
+		committedValue := value(42)
+
+		// Initialise the round
+		currentRound.start()
+
+		// Proposal timeout
+		currentRound.processTimeout(types.StepPropose).expectActions(
+			currentRound.action().broadcastPrevote(nil),
+		)
+
+		// Prevotes are collected
+		currentRound.validator(1).prevote(&committedValue).expectActions()
+		currentRound.validator(2).prevote(&committedValue).expectActions(
+			currentRound.action().scheduleTimeout(types.StepPrevote),
+		)
+		currentRound.processTimeout(types.StepPrevote).expectActions(
+			currentRound.action().broadcastPrecommit(nil),
+		)
+		currentRound.validator(0).prevote(&committedValue).expectActions()
+
+		// Receives precommits, this rule shouldn't block the commit value rule
+		currentRound.validator(1).precommit(&committedValue)
+		currentRound.validator(2).precommit(&committedValue)
+		currentRound.validator(0).precommit(&committedValue)
+		currentRound.validator(0).proposal(committedValue, -1).expectActions(
+			currentRound.action().commit(committedValue, -1, 0),
+			nextRound.action().scheduleTimeout(types.StepPropose),
+		)
+
+		assertState(t, stateMachine, types.Height(1), types.Round(0), types.StepPropose)
+	})
+
 	t.Run("Line 36: record valid value even if we don't prevote it", func(t *testing.T) {
 		stateMachine := setupStateMachine(t, 4, 1)
 		currentRound := newTestRound(t, stateMachine, 0, 0)