Somehow missed a dep form Yarn...

package.json

@@ -26,6 +26,7 @@
   "dependencies": {
     "css-loader": "^0.27.3",
     "jest": "^19.0.2",
+    "jest-vue-preprocessor": "^0.1.3",
     "marked": "^0.3.6",
     "vue": "^2.2.4",
     "vue-loader": "^11.1.4",

yarn.lock

@@ -575,6 +575,12 @@ babel-plugin-transform-regenerator@^6.22.0:
   dependencies:
     regenerator-transform "0.9.8"
+babel-plugin-transform-runtime@^6.23.0:
+  version "6.23.0"
+  resolved "https://registry.yarnpkg.com/babel-plugin-transform-runtime/-/babel-plugin-transform-runtime-6.23.0.tgz#88490d446502ea9b8e7efb0fe09ec4d99479b1ee"
+  dependencies:
+    babel-runtime "^6.22.0"
+
 babel-plugin-transform-strict-mode@^6.22.0:
   version "6.22.0"
   resolved "https://registry.yarnpkg.com/babel-plugin-transform-strict-mode/-/babel-plugin-transform-strict-mode-6.22.0.tgz#e008df01340fdc87e959da65991b7e05970c8c7c"
@@ -2164,6 +2170,12 @@ jest-validate@^19.0.2:
     leven "^2.0.0"
     pretty-format "^19.0.0"
+jest-vue-preprocessor@^0.1.3:
+  version "0.1.3"
+  resolved "https://registry.yarnpkg.com/jest-vue-preprocessor/-/jest-vue-preprocessor-0.1.3.tgz#287b5075f916090b9104818d581e6a0c73241b08"
+  dependencies:
+    babel-plugin-transform-runtime "^6.23.0"
+
 jest@^19.0.2:
   version "19.0.2"
   resolved "https://registry.yarnpkg.com/jest/-/jest-19.0.2.tgz#b794faaf8ff461e7388f28beef559a54f20b2c10"