fix lint errors

[CodingSolo]

get errors when run yarn lint:

$ yarn lint
yarn run v1.17.3
$ cross-env NODE_ENV=development eslint --cache --format=node_modules/eslint-formatter-pretty .

  app/components/tools/Editor.js:164:14
  ⚠  164:14  Unexpected constant condition.                                      no-constant-condition

  app/components/middle/Item.js:188:31
  ✖  188:31  item.color is missing in props validation                           react/prop-types

  test/containers/CounterPage.spec.js:7:25
  ✖    7:25  Missing file extension for "../../app/containers/CounterPage"       import/extensions
  ✖    7:25  Unable to resolve path to module ../../app/containers/CounterPage.  import/no-unresolved

  test/components/Counter.spec.js:7:21
  ✖    7:21  Missing file extension for "../../app/components/Counter"           import/extensions
  ✖    7:21  Unable to resolve path to module ../../app/components/Counter.      import/no-unresolved

  test/actions/counter.spec.js:2:26
  ✖    2:26  Missing file extension for "../../app/actions/counter"              import/extensions
  ✖    2:26  Unable to resolve path to module ../../app/actions/counter.         import/no-unresolved

  app/components/ExportDialog.js:117:64
  ⚠  117:64  Unexpected unnamed function.                                        func-names
  ✖  117:64  Unexpected function expression.                                     prefer-arrow-callback
  ✖  117:79  result is defined but never used.                                   no-unused-vars

  test/reducers/counter.spec.js:1:21
  ✖    1:21  Missing file extension for "../../app/reducers/counter"             import/extensions
  ✖    1:21  Unable to resolve path to module ../../app/reducers/counter.        import/no-unresolved
  ✖    5:8   Missing file extension for "../../app/actions/counter"              import/extensions
  ✖    5:8   Unable to resolve path to module ../../app/actions/counter.         import/no-unresolved

  2 warnings
  13 errors

rename the sample test files and fix 2 errors: