Prevent unit/integration tests from running against stale build artifacts (#55)

Closes #54.

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## This PR is a:

[ ] New feature
[ ] Enhancement/Optimization
[ ] Refactor
[X] Bugfix
[ ] Test for existing code
[ ] Documentation

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## Summary

See #54 .
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## Additional information

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Author: DrewML

.circleci/config.yml

@@ -13,7 +13,10 @@ jobs:
           - v1-npm-cache-{{ .Branch }}
           - v1-npm-cache-
 
-      # Install root devDependencies and bootstrap packages
+      # Install root devDependencies and bootstrap packages. We use
+      # --ignore-scripts to prevent building any artifacts to disk prior
+      # to running Jest. This is a safeguard to ensure our tests always operate
+      # on the latest source
       - run:
           name: Install shared devDependencies
           command: 'npm install --ignore-scripts'

packages/venia-concept/jest.config.js

@@ -1,8 +1,21 @@
+const { join } = require('path');
+
 module.exports = {
     displayName: 'Venia Concept',
     browser: true,
     moduleNameMapper: {
         '\\.css$': 'identity-obj-proxy',
-        '^src/(.+)': '<rootDir>/src/$1'
-    }
+        // Mirrors webpack alias to resolve from 'src'
+        '^src/(.+)': '<rootDir>/src/$1',
+        // Re-write imports to Peregrine to ensure they're not pulled from the
+        // (possibly outdated) build artifacts on disk in `dist`.
+        // Ideally this rule would be in the root Jest config, but Jest's config
+        // merging strategy isn't currently smart enough for this. TODO: Look
+        // into moving to root config in later versions of Jest if config merging
+        // improves
+        '^@magento/peregrine(/*(?:.+)*)': join(__dirname, '../peregrine/src/$1')
+    },
+    // Have Jest use Babel to transpile Peregrine imports in tests, since
+    // our cross-package tests in the monorepo should all operate on `src`
+    transformIgnorePatterns: ['node_modules/(?!@magento/peregrine)']
 };

packages/venia-concept/package-lock.json

@@ -16,7 +16,7 @@
     "start:debug": "node --inspect-brk ./node_modules/.bin/webpack-dev-server --progress --color --env.phase development"
   },
   "dependencies": {
-    "@magento/peregrine": "^0.3.0",
+    "@magento/peregrine": "^0.4.0",
     "babel-runtime": "^6.26.0",
     "dotenv": "^4.0.0",
     "feather-icons": "^4.6.0",