Fill-in skipped blocks on page render for blocks list and homepage

apps/block_scout_web/assets/__tests__/pages/block.js

@@ -1,6 +1,5 @@
 import { reducer, initialState } from '../../js/pages/block'
 
-
 test('CHANNEL_DISCONNECTED', () => {
   const state = initialState
   const action = {
@@ -11,6 +10,61 @@ test('CHANNEL_DISCONNECTED', () => {
   expect(output.channelDisconnected).toBe(true)
 })
 
+describe('PAGE_LOAD', () => {
+  test('page 1 loads block numbers', () => {
+    const state = initialState
+    const action = {
+      type: 'PAGE_LOAD',
+      beyondPageOne: false,
+      blockNumbers: [2, 1]
+    }
+    const output = reducer(state, action)
+
+    expect(output.beyondPageOne).toBe(false)
+    expect(output.blockNumbers).toEqual([2, 1])
+    expect(output.skippedBlockNumbers).toEqual([])
+  })
+  test('page 2 loads block numbers', () => {
+    const state = initialState
+    const action = {
+      type: 'PAGE_LOAD',
+      beyondPageOne: true,
+      blockNumbers: [2, 1]
+    }
+    const output = reducer(state, action)
+
+    expect(output.beyondPageOne).toBe(true)
+    expect(output.blockNumbers).toEqual([2, 1])
+    expect(output.skippedBlockNumbers).toEqual([])
+  })
+  test('page 1 with skipped blocks', () => {
+    const state = initialState
+    const action = {
+      type: 'PAGE_LOAD',
+      beyondPageOne: false,
+      blockNumbers: [4, 1]
+    }
+    const output = reducer(state, action)
+
+    expect(output.beyondPageOne).toBe(false)
+    expect(output.blockNumbers).toEqual([4, 3, 2, 1])
+    expect(output.skippedBlockNumbers).toEqual([3, 2])
+  })
+  test('page 2 with skipped blocks', () => {
+    const state = initialState
+    const action = {
+      type: 'PAGE_LOAD',
+      beyondPageOne: true,
+      blockNumbers: [4, 1]
+    }
+    const output = reducer(state, action)
+
+    expect(output.beyondPageOne).toBe(true)
+    expect(output.blockNumbers).toEqual([4, 3, 2, 1])
+    expect(output.skippedBlockNumbers).toEqual([3, 2])
+  })
+})
+
 describe('RECEIVED_NEW_BLOCK', () => {
   test('receives new block', () => {
     const action = {
@@ -56,12 +110,12 @@ describe('RECEIVED_NEW_BLOCK', () => {
 
     expect(output.newBlock).toBe('test5')
     expect(output.blockNumbers).toEqual([5, 4, 3, 2])
-    expect(output.skippedBlockNumbers).toEqual([3, 4])
+    expect(output.skippedBlockNumbers).toEqual([4, 3])
   })
   test('replaces skipped block', () => {
     const state = Object.assign({}, initialState, {
       blockNumbers: [5, 4, 3, 2, 1],
-      skippedBlockNumbers: [1, 3, 4]
+      skippedBlockNumbers: [4, 3, 1]
     })
     const action = {
       type: 'RECEIVED_NEW_BLOCK',
@@ -74,7 +128,7 @@ describe('RECEIVED_NEW_BLOCK', () => {
 
     expect(output.newBlock).toBe('test3')
     expect(output.blockNumbers).toEqual([5, 4, 3, 2, 1])
-    expect(output.skippedBlockNumbers).toEqual([1, 4])
+    expect(output.skippedBlockNumbers).toEqual([4, 1])
   })
   test('replaces duplicated block', () => {
     const state = Object.assign({}, initialState, {

apps/block_scout_web/assets/__tests__/pages/chain.js

@@ -1,5 +1,30 @@
 import { reducer, initialState } from '../../js/pages/chain'
 
+describe('PAGE_LOAD', () => {
+  test('loads block numbers', () => {
+    const state = initialState
+    const action = {
+      type: 'PAGE_LOAD',
+      blockNumbers: [2, 1]
+    }
+    const output = reducer(state, action)
+
+    expect(output.blockNumbers).toEqual([2, 1])
+    expect(output.skippedBlockNumbers).toEqual([])
+  })
+  test('loads with skipped blocks', () => {
+    const state = initialState
+    const action = {
+      type: 'PAGE_LOAD',
+      blockNumbers: [4, 1]
+    }
+    const output = reducer(state, action)
+
+    expect(output.blockNumbers).toEqual([4, 3, 2, 1])
+    expect(output.skippedBlockNumbers).toEqual([3, 2])
+  })
+})
+
 test('RECEIVED_NEW_ADDRESS_COUNT', () => {
   const state = Object.assign({}, initialState, {
     addressCount: '1,000'
@@ -54,12 +79,12 @@ describe('RECEIVED_NEW_BLOCK', () => {
     expect(output.averageBlockTime).toEqual('5 seconds')
     expect(output.newBlock).toBe('test5')
     expect(output.blockNumbers).toEqual([5, 4, 3, 2])
-    expect(output.skippedBlockNumbers).toEqual([3, 4])
+    expect(output.skippedBlockNumbers).toEqual([4, 3])
   })
   test('replaces skipped block', () => {
     const state = Object.assign({}, initialState, {
       blockNumbers: [4, 3, 2, 1],
-      skippedBlockNumbers: [1, 2, 3]
+      skippedBlockNumbers: [3, 2, 1]
     })
     const action = {
       type: 'RECEIVED_NEW_BLOCK',
@@ -74,7 +99,7 @@ describe('RECEIVED_NEW_BLOCK', () => {
     expect(output.averageBlockTime).toEqual('5 seconds')
     expect(output.newBlock).toBe('test2')
     expect(output.blockNumbers).toEqual([4, 3, 2, 1])
-    expect(output.skippedBlockNumbers).toEqual([1, 3])
+    expect(output.skippedBlockNumbers).toEqual([3, 1])
   })
   test('replaces duplicated block', () => {
     const state = Object.assign({}, initialState, {
@@ -116,7 +141,7 @@ describe('RECEIVED_NEW_BLOCK', () => {
   test('only tracks 4 blocks based on page display limit', () => {
     const state = Object.assign({}, initialState, {
       blockNumbers: [5, 4, 3, 2],
-      skippedBlockNumbers: [2, 3, 4]
+      skippedBlockNumbers: [4, 3, 2]
     })
     const action = {
       type: 'RECEIVED_NEW_BLOCK',
@@ -129,12 +154,12 @@ describe('RECEIVED_NEW_BLOCK', () => {
 
     expect(output.newBlock).toBe('test6')
     expect(output.blockNumbers).toEqual([6, 5, 4, 3])
-    expect(output.skippedBlockNumbers).toEqual([3, 4])
+    expect(output.skippedBlockNumbers).toEqual([4, 3])
   })
   test('skipped blocks list replaced when another block comes in with +3 blockheight', () => {
     const state = Object.assign({}, initialState, {
       blockNumbers: [5, 4, 3, 2],
-      skippedBlockNumbers: [2, 3, 4]
+      skippedBlockNumbers: [4, 3, 2]
     })
     const action = {
       type: 'RECEIVED_NEW_BLOCK',
@@ -147,7 +172,7 @@ describe('RECEIVED_NEW_BLOCK', () => {
 
     expect(output.newBlock).toBe('test10')
     expect(output.blockNumbers).toEqual([10, 9, 8, 7])
-    expect(output.skippedBlockNumbers).toEqual([7, 8, 9])
+    expect(output.skippedBlockNumbers).toEqual([9, 8, 7])
   })
 })
 

apps/block_scout_web/assets/css/components/_tile.scss

@@ -17,7 +17,7 @@
 
   &-type {
 
-    &-Block {
+    &-block {
       border-left: 4px solid $indigo;
 
       .tile-label {
@@ -25,7 +25,7 @@
       }
     }
 
-    &-Uncle {
+    &-uncle {
       border-left: 4px solid $cyan;
 
       .tile-label {
@@ -33,7 +33,7 @@
       }
     }
 
-    &-Reorg {
+    &-reorg {
       border-left: 4px solid $purple;
 
       .tile-label {

apps/block_scout_web/assets/js/pages/block.js

@@ -4,7 +4,7 @@ import URI from 'urijs'
 import humps from 'humps'
 import socket from '../socket'
 import { updateAllAges } from '../lib/from_now'
-import { initRedux, prependWithClingBottom } from '../utils'
+import { buildFullBlockList, initRedux, beforeWithClingBottom, skippedBlockListBuilder } from '../utils'
 
 export const initialState = {
   blockNumbers: [],
@@ -18,9 +18,12 @@ export const initialState = {
 export function reducer (state = initialState, action) {
   switch (action.type) {
     case 'PAGE_LOAD': {
+      const blockNumbers = buildFullBlockList(action.blockNumbers)
+      const skippedBlockNumbers = _.difference(blockNumbers, action.blockNumbers)
       return Object.assign({}, state, {
         beyondPageOne: action.beyondPageOne,
-        blockNumbers: action.blockNumbers
+        blockNumbers,
+        skippedBlockNumbers
       })
     }
     case 'CHANNEL_DISCONNECTED': {
@@ -43,9 +46,7 @@ export function reducer (state = initialState, action) {
       } else {
         let skippedBlockNumbers = state.skippedBlockNumbers.slice(0)
         if (blockNumber > state.blockNumbers[0] + 1) {
-          for (let i = state.blockNumbers[0] + 1; i < blockNumber; i++) {
-            skippedBlockNumbers.push(i)
-          }
+          skippedBlockListBuilder(skippedBlockNumbers, blockNumber, state.blockNumbers[0])
         }
         const newBlockNumbers = _.chain([blockNumber])
           .union(skippedBlockNumbers, state.blockNumbers)
@@ -85,22 +86,21 @@ if ($blockListPage.length) {
     },
     render (state, oldState) {
       const $channelDisconnected = $('[data-selector="channel-disconnected-message"]')
-      const $blocksList = $('[data-selector="blocks-list"]')
+      const skippedBlockNumbers = _.difference(state.skippedBlockNumbers, oldState.skippedBlockNumbers)
 
       if (state.channelDisconnected) $channelDisconnected.show()
-      if (oldState.newBlock !== state.newBlock || (state.replaceBlock && oldState.replaceBlock !== state.replaceBlock)) {
+      if ((state.newBlock && oldState.newBlock !== state.newBlock) || skippedBlockNumbers.length) {
         if (state.replaceBlock && oldState.replaceBlock !== state.replaceBlock) {
           const $replaceBlock = $(`[data-block-number="${state.replaceBlock}"]`)
           $replaceBlock.addClass('shrink-out')
           setTimeout(() => $replaceBlock.replaceWith(state.newBlock), 400)
         } else {
-          if (oldState.skippedBlockNumbers !== state.skippedBlockNumbers) {
-            const newSkippedBlockNumbers = _.difference(state.skippedBlockNumbers, oldState.skippedBlockNumbers)
-            _.map(newSkippedBlockNumbers, (skippedBlockNumber) => {
-              prependWithClingBottom($blocksList, placeHolderBlock(skippedBlockNumber))
+          if (skippedBlockNumbers.length) {
+            _.forEachRight(skippedBlockNumbers, (skippedBlockNumber) => {
+              beforeWithClingBottom($(`[data-block-number="${skippedBlockNumber - 1}"]`), placeHolderBlock(skippedBlockNumber))
             })
           }
-          prependWithClingBottom($blocksList, state.newBlock)
+          beforeWithClingBottom($(`[data-block-number="${state.blockNumbers[0] - 1}"]`), state.newBlock)
         }
         updateAllAges()
       }
@@ -110,11 +110,10 @@ if ($blockListPage.length) {
 
 function placeHolderBlock (blockNumber) {
   return `
-    <div class="my-3">
+    <div class="my-3" style="height: 98px;" data-selector="place-holder" data-block-number="${blockNumber}">
       <div
         class="tile tile-type-block d-flex align-items-center fade-up"
-        data-selector="place-holder"
-        data-block-number="${blockNumber}"
+        style="height: 98px;"
       >
         <span class="loading-spinner-small ml-1 mr-4">
           <span class="loading-spinner-block-1"></span>

apps/block_scout_web/assets/js/pages/chain.js

@@ -5,7 +5,7 @@ import numeral from 'numeral'
 import socket from '../socket'
 import { updateAllAges } from '../lib/from_now'
 import { exchangeRateChannel, formatUsdValue } from '../lib/currency'
-import { batchChannel, initRedux, slideDownPrepend } from '../utils'
+import { batchChannel, buildFullBlockList, initRedux, skippedBlockListBuilder, slideDownPrepend } from '../utils'
 import { createMarketHistoryChart } from '../lib/market_history_chart'
 
 const BATCH_THRESHOLD = 10
@@ -28,9 +28,13 @@ export const initialState = {
 export function reducer (state = initialState, action) {
   switch (action.type) {
     case 'PAGE_LOAD': {
+      const fullBlockNumberList = buildFullBlockList(action.blockNumbers)
+      const fullSkippedBlockNumberList = _.difference(fullBlockNumberList, action.blockNumbers)
+      const blockNumbers = fullBlockNumberList.slice(0, 4)
       return Object.assign({}, state, {
-        blockNumbers: action.blockNumbers,
-        transactionCount: numeral(action.transactionCount).value()
+        blockNumbers,
+        transactionCount: numeral(action.transactionCount).value(),
+        skippedBlockNumbers: _.intersection(fullSkippedBlockNumberList, blockNumbers)
       })
     }
     case 'RECEIVED_NEW_ADDRESS_COUNT': {
@@ -52,21 +56,18 @@ export function reducer (state = initialState, action) {
       } else {
         let skippedBlockNumbers = state.skippedBlockNumbers.slice(0)
         if (blockNumber > state.blockNumbers[0] + 1) {
-          let lastPlaceholder = state.blockNumbers[0] + 1
-          if (blockNumber - lastPlaceholder > 3) {
-            lastPlaceholder = blockNumber - 3
+          let oldestBlock = state.blockNumbers[0]
+          if (blockNumber - oldestBlock >= 3) {
             skippedBlockNumbers = []
+            if (blockNumber - oldestBlock > 3) oldestBlock = blockNumber - 4
           }
-          for (let i = lastPlaceholder; i < blockNumber; i++) {
-            skippedBlockNumbers.push(i)
-          }
+          skippedBlockListBuilder(skippedBlockNumbers, blockNumber, oldestBlock)
         }
         const newBlockNumbers = _.chain([blockNumber])
           .union(skippedBlockNumbers, state.blockNumbers)
           .orderBy([], ['desc'])
           .slice(0, 4)
           .value()
-
         const newSkippedBlockNumbers = _.intersection(skippedBlockNumbers, newBlockNumbers)
         return Object.assign({}, state, {
           averageBlockTime: action.msg.averageBlockTime,
@@ -142,6 +143,8 @@ if ($chainDetailsPage.length) {
       const $marketCap = $('[data-selector="market-cap"]')
       const $transactionsList = $('[data-selector="transactions-list"]')
       const $transactionCount = $('[data-selector="transaction-count"]')
+      const newTransactions = _.difference(state.newTransactions, oldState.newTransactions)
+      const skippedBlockNumbers = _.difference(state.skippedBlockNumbers, oldState.skippedBlockNumbers)
 
       if (oldState.addressCount !== state.addressCount) {
         $addressCount.empty().append(state.addressCount)
@@ -152,24 +155,23 @@ if ($chainDetailsPage.length) {
       if (oldState.usdMarketCap !== state.usdMarketCap) {
         $marketCap.empty().append(formatUsdValue(state.usdMarketCap))
       }
-      if (state.newBlock && oldState.newBlock !== state.newBlock) {
+      if ((state.newBlock && oldState.newBlock !== state.newBlock) || skippedBlockNumbers.length) {
         if (state.replaceBlock && oldState.replaceBlock !== state.replaceBlock) {
           const $replaceBlock = $(`[data-block-number="${state.replaceBlock}"]`)
           $replaceBlock.addClass('shrink-out')
           setTimeout(() => $replaceBlock.replaceWith(state.newBlock), 400)
         } else {
-          if (oldState.skippedBlockNumbers !== state.skippedBlockNumbers) {
-            const newSkippedBlockNumbers = _.chain(state.skippedBlockNumbers)
-              .difference(oldState.skippedBlockNumbers)
-              .intersection(state.blockNumbers)
-              .value()
-            _.map(newSkippedBlockNumbers, (skippedBlockNumber) => {
+          if (state.newBlock) {
             $blockList.children().last().remove()
-              $blockList.prepend(placeHolderBlock(skippedBlockNumber))
-            })
+            $blockList.prepend(newBlockHtml(state.newBlock))
           }
+          if (skippedBlockNumbers.length) {
+            const newSkippedBlockNumbers = _.intersection(skippedBlockNumbers, state.blockNumbers)
+            _.each(newSkippedBlockNumbers, (skippedBlockNumber) => {
               $blockList.children().last().remove()
-          $blockList.prepend(newBlockHtml(state.newBlock))
+              $(`[data-block-number="${skippedBlockNumber + 1}"]`).parent().after(placeHolderBlock(skippedBlockNumber))
+            })
+          }
         }
         updateAllAges()
       }
@@ -180,7 +182,7 @@ if ($chainDetailsPage.length) {
       } else {
         $channelBatching.hide()
       }
-      if (oldState.newTransactions !== state.newTransactions) {
+      if (newTransactions.length) {
         const newTransactionsToInsert = state.newTransactions.slice(oldState.newTransactions.length)
         $transactionsList
           .children()
@@ -190,7 +192,6 @@ if ($chainDetailsPage.length) {
 
         updateAllAges()
       }
-
       if (oldState.availableSupply !== state.availableSupply || oldState.marketHistoryData !== state.marketHistoryData) {
         chart.update(state.availableSupply, state.marketHistoryData)
       }
@@ -214,9 +215,9 @@ function placeHolderBlock (blockNumber) {
     >
       <div
         class="tile tile-type-block d-flex align-items-center fade-up"
+        style="height: 100px;"
         data-selector="place-holder"
         data-block-number="${blockNumber}"
-        style="height: 100px;"
       >
         <span class="loading-spinner-small ml-1 mr-4">
           <span class="loading-spinner-block-1"></span>

apps/block_scout_web/assets/js/utils.js

@@ -14,6 +14,12 @@ export function batchChannel (func) {
   }
 }
 
+export function buildFullBlockList (blockNumbers) {
+  const newestBlock = _.first(blockNumbers)
+  const oldestBlock = _.last(blockNumbers)
+  return skippedBlockListBuilder([], newestBlock + 1, oldestBlock - 1)
+}
+
 export function initRedux (reducer, { main, render, debug } = {}) {
   if (!reducer) {
     console.error('initRedux: You need a reducer to initialize Redux.')
@@ -34,16 +40,33 @@ export function initRedux (reducer, { main, render, debug } = {}) {
   if (main) main(store)
 }
 
+export function skippedBlockListBuilder (skippedBlockNumbers, newestBlock, oldestBlock) {
+  for (let i = newestBlock - 1; i > oldestBlock; i--) skippedBlockNumbers.push(i)
+  return skippedBlockNumbers
+}
+
 export function slideDownPrepend ($el, content, callback) {
   const $content = $(content)
   $el.prepend($content.hide())
   $content.slideDown({ complete: callback })
 }
+export function slideDownBefore ($el, content, callback) {
+  const $content = $(content)
+  $el.before($content.hide())
+  $content.slideDown({ complete: callback })
+}
 export function prependWithClingBottom ($el, content) {
+  return slideDownPrepend($el, content, clingBottom($el, content))
+}
+export function beforeWithClingBottom ($el, content) {
+  return slideDownBefore($el, content, clingBottom($el, content))
+}
+
+function clingBottom ($el, content) {
   function userAtTop () {
     return window.scrollY < $('[data-selector="navbar"]').outerHeight()
   }
-  if (userAtTop()) return slideDownPrepend($el, content)
+  if (userAtTop()) return true
 
   let isAnimating
   function setIsAnimating () {
@@ -73,8 +96,10 @@ export function prependWithClingBottom ($el, content) {
     $el.off('animationend animationcancel', stopClinging)
   }
 
-  return slideDownPrepend($el, content, () => {
+  return {
+    function () {
       $el.on('animationend animationcancel', stopClinging)
       setTimeout(() => !isAnimating && stopClinging(), 100)
-  })
+    }
+  }
 }

apps/block_scout_web/test/block_scout_web/features/pages/block_list_page.ex

@@ -20,7 +20,7 @@ defmodule BlockScoutWeb.BlockListPage do
   end
 
   def block(%Block{number: block_number}) do
-    css("[data-selector='block-tile'][data-block-number='#{block_number}']")
+    css("[data-block-number='#{block_number}']")
   end
 
   def place_holder_blocks(count) do

apps/block_scout_web/test/block_scout_web/features/pages/chain_page.ex

@@ -5,7 +5,11 @@ defmodule BlockScoutWeb.ChainPage do
 
   import Wallaby.Query, only: [css: 1, css: 2]
 
-  alias Explorer.Chain.Transaction
+  alias Explorer.Chain.{Block, Transaction}
+
+  def block(%Block{number: block_number}) do
+    css("[data-block-number='#{block_number}']")
+  end
 
   def blocks(count: count) do
     css("[data-selector='chain-block']", count: count)
@@ -15,6 +19,10 @@ defmodule BlockScoutWeb.ChainPage do
     css("[data-test='contract-creation'] [data-address-hash='#{hash}']")
   end
 
+  def place_holder_blocks(count) do
+    css("[data-selector='place-holder']", count: count)
+  end
+
   def search(session, text) do
     session
     |> fill_in(css("[data-test='search_input']"), with: text)

apps/block_scout_web/test/block_scout_web/features/viewing_blocks_test.exs

@@ -2,6 +2,7 @@ defmodule BlockScoutWeb.ViewingBlocksTest do
   use BlockScoutWeb.FeatureCase, async: true
 
   alias BlockScoutWeb.{BlockListPage, BlockPage, Notifier}
+  alias Explorer.Chain.Block
 
   setup do
     timestamp = Timex.now() |> Timex.shift(hours: -1)
@@ -159,6 +160,28 @@ defmodule BlockScoutWeb.ViewingBlocksTest do
       |> assert_has(BlockListPage.block(skipped_block))
       |> assert_has(BlockListPage.place_holder_blocks(2))
     end
+
+    test "inserts place holder blocks on render for out of order blocks", %{session: session} do
+      insert(:block, number: 315)
+
+      session
+      |> BlockListPage.visit_page()
+      |> assert_has(BlockListPage.block(%Block{number: 314}))
+      |> assert_has(BlockListPage.place_holder_blocks(3))
+    end
+
+    test "replaces rendered place holder block if skipped block received", %{session: session} do
+      insert(:block, number: 315)
+
+      BlockListPage.visit_page(session)
+
+      block = insert(:block, number: 314)
+      Notifier.handle_event({:chain_event, :blocks, [block]})
+
+      session
+      |> assert_has(BlockListPage.block(block))
+      |> assert_has(BlockListPage.place_holder_blocks(2))
+    end
   end
 
   describe "viewing uncle blocks list" do

apps/block_scout_web/test/block_scout_web/features/viewing_chain_test.exs

@@ -3,7 +3,8 @@ defmodule BlockScoutWeb.ViewingChainTest do
 
   use BlockScoutWeb.FeatureCase, async: true
 
-  alias BlockScoutWeb.{AddressPage, BlockPage, ChainPage, TransactionPage}
+  alias BlockScoutWeb.{AddressPage, BlockPage, ChainPage, Notifier, TransactionPage}
+  alias Explorer.Chain.Block
 
   setup do
     Enum.map(401..404, &insert(:block, number: &1))
@@ -50,6 +51,57 @@ defmodule BlockScoutWeb.ViewingChainTest do
       |> ChainPage.visit_page()
       |> assert_has(ChainPage.blocks(count: 4))
     end
+
+    test "inserts place holder blocks if out of order block received", %{session: session} do
+      ChainPage.visit_page(session)
+
+      block = insert(:block, number: 409)
+      Notifier.handle_event({:chain_event, :blocks, :realtime, [block]})
+
+      session
+      |> assert_has(ChainPage.block(block))
+      |> assert_has(ChainPage.place_holder_blocks(3))
+    end
+
+    test "replaces place holder block if skipped block received", %{session: session} do
+      ChainPage.visit_page(session)
+
+      block = insert(:block, number: 409)
+      Notifier.handle_event({:chain_event, :blocks, :realtime, [block]})
+
+      session
+      |> assert_has(ChainPage.block(block))
+      |> assert_has(ChainPage.place_holder_blocks(3))
+
+      skipped_block = insert(:block, number: 408)
+      Notifier.handle_event({:chain_event, :blocks, :realtime, [skipped_block]})
+
+      session
+      |> assert_has(ChainPage.block(skipped_block))
+      |> assert_has(ChainPage.place_holder_blocks(2))
+    end
+
+    test "inserts place holder blocks on render for out of order blocks", %{session: session} do
+      insert(:block, number: 409)
+
+      session
+      |> ChainPage.visit_page()
+      |> assert_has(ChainPage.block(%Block{number: 408}))
+      |> assert_has(ChainPage.place_holder_blocks(3))
+    end
+
+    test "replaces rendered place holder block if skipped block received", %{session: session} do
+      insert(:block, number: 409)
+
+      ChainPage.visit_page(session)
+
+      block = insert(:block, number: 408)
+      Notifier.handle_event({:chain_event, :blocks, [block]})
+
+      session
+      |> assert_has(ChainPage.block(block))
+      |> assert_has(ChainPage.place_holder_blocks(2))
+    end
   end
 
   describe "viewing transactions" do