tests: reduce validator network size to less than 2F+1

tests/dynamic_test.go

@@ -149,4 +149,36 @@ var _ = Describe("Dynamic validators addition/removal testing", func() {
 			})
 		})
 	})
+
+	It("TFS-02-05 Reduce validator network size below 2F+1", func() {
+		By("Ensure that blocks are generated by validators", func() {
+			waitFor(blockchain.Validators(), func(geth container.Ethereum, wg *sync.WaitGroup) {
+				Expect(geth.WaitForBlocks(5)).To(BeNil())
+				wg.Done()
+			})
+		})
+
+		By("Reduce validator network size to less than 2F+1", func() {
+			stopCandidates := blockchain.Validators()[numberOfValidators-2:]
+			// stop validators [3,4]
+			for _, candidates := range stopCandidates {
+				c := candidates.NewIstanbulClient()
+				Expect(c.StopMining(context.Background())).Should(BeNil())
+			}
+		})
+
+		By("Verify number of validators", func() {
+			for _, v := range blockchain.Validators() {
+				client := v.NewIstanbulClient()
+				validators, err := client.GetValidators(context.Background(), nil)
+				Expect(err).Should(BeNil())
+				Expect(len(validators)).Should(BeNumerically("==", numberOfValidators))
+			}
+		})
+
+		By("No block generated", func() {
+			// REMARK: ErrNoBlock will return if validators not generate block after 10 second.
+			Expect(blockchain.EnsureConsensusWorking(blockchain.Validators(), 11*time.Second)).Should(Equal(container.ErrNoBlock))
+		})
+	})
 })