TypeError invoking getElementsByName and getTotalLength

[alexieyizhe]

While using Jest + Enzyme/ReactTestRenderer, I encountered the two following errors:

Renderer:

TypeError: Cannot read property 'getElementsByTagName' of null

      at MtSvgLines.selectPathElems (node_modules/react-mt-svg-lines/lib/index.js:282:36)
      at MtSvgLines.getPathLengths (node_modules/react-mt-svg-lines/lib/index.js:373:28)
      at MtSvgLines.animate (node_modules/react-mt-svg-lines/lib/index.js:229:34)
      at MtSvgLines.componentDidMount (node_modules/react-mt-svg-lines/lib/index.js:96:12)
      at node_modules/react-test-renderer/lib/ReactCompositeComponent.js:262:25
      at measureLifeCyclePerf (node_modules/react-test-renderer/lib/ReactCompositeComponent.js:73:12)
      at node_modules/react-test-renderer/lib/ReactCompositeComponent.js:261:11
      at CallbackQueue.notifyAll (node_modules/react-test-renderer/lib/CallbackQueue.js:74:22)
      at ReactTestReconcileTransaction.close (node_modules/react-test-renderer/lib/ReactTestReconcileTransaction.js:34:26)
      at ReactTestReconcileTransaction.closeAll (node_modules/react-test-renderer/lib/Transaction.js:207:25)
      at ReactTestReconcileTransaction.perform (node_modules/react-test-renderer/lib/Transaction.js:154:16)
      at batchedMountComponentIntoNode (node_modules/react-test-renderer/lib/ReactTestMount.js:67:27)
      at ReactDefaultBatchingStrategyTransaction.perform (node_modules/react-test-renderer/lib/Transaction.js:141:20)
      at Object.batchedUpdates (node_modules/react-test-renderer/lib/ReactDefaultBatchingStrategy.js:60:26)
      at Object.batchedUpdates (node_modules/react-test-renderer/lib/ReactUpdates.js:95:27)
      at Object.render (node_modules/react-test-renderer/lib/ReactTestMount.js:126:18)
      at Object.<anonymous> (tests/PageFooter.test.js:28:32)

Enzyme (same as #11 ):

TypeError: pathEl.getTotalLength is not a function

      at node_modules/react-mt-svg-lines/lib/index.js:375:89
          at Proxy.map (<anonymous>)
      at MtSvgLines.getPathLengths (node_modules/react-mt-svg-lines/lib/index.js:374:21)
      at MtSvgLines.animate (node_modules/react-mt-svg-lines/lib/index.js:229:34)
      at MtSvgLines.componentDidMount (node_modules/react-mt-svg-lines/lib/index.js:96:12)
      at node_modules/react-dom/lib/ReactCompositeComponent.js:262:25
      at measureLifeCyclePerf (node_modules/react-dom/lib/ReactCompositeComponent.js:73:12)
      at node_modules/react-dom/lib/ReactCompositeComponent.js:261:11
      at CallbackQueue.notifyAll (node_modules/react-dom/lib/CallbackQueue.js:74:22)
      at ReactReconcileTransaction.close (node_modules/react-dom/lib/ReactReconcileTransaction.js:78:26)
      at ReactReconcileTransaction.closeAll (node_modules/react-dom/lib/Transaction.js:207:25)
      at ReactReconcileTransaction.perform (node_modules/react-dom/lib/Transaction.js:154:16)
      at batchedMountComponentIntoNode (node_modules/react-dom/lib/ReactMount.js:124:15)
      at ReactDefaultBatchingStrategyTransaction.perform (node_modules/react-dom/lib/Transaction.js:141:20)
      at Object.batchedUpdates (node_modules/react-dom/lib/ReactDefaultBatchingStrategy.js:60:26)
      at Object.batchedUpdates (node_modules/react-dom/lib/ReactUpdates.js:95:27)
      at Object._renderNewRootComponent (node_modules/react-dom/lib/ReactMount.js:317:18)
      at Object._renderSubtreeIntoContainer (node_modules/react-dom/lib/ReactMount.js:399:32)
      at Object.render (node_modules/react-dom/lib/ReactMount.js:420:23)
      at Object.render (node_modules/enzyme-adapter-react-15/build/ReactFifteenAdapter.js:181:50)
      at new ReactWrapper (node_modules/enzyme/build/ReactWrapper.js:98:16)
      at mount (node_modules/enzyme/build/mount.js:19:10)
      at Object.<anonymous> (tests/PageFooter.test.js:22:14)

I'm using react-mt-svg-lines 0.8.4, and right now I'm working around this issue by safely accessing getElementsByTagName through this change to line 282 in index.js:
var svgEl = this._svgWrapper && this._svgWrapper.getElementsByTagName('svg')[0];

[moarwick]

k, don't have a quick way to test it with Enzyme/ReactTestRenderer but your guard looks good. implemented in 0.8.5. will need to make a larger update for React 17 soon, so perhaps will find some time to add Jest/Enzyme then..