start adding test framework

lib/settings-loader.js

@@ -1,15 +1,41 @@
+const path = require('path')
+const fs = require('fs')
+
 const _ = require('lodash/fp')
+const argv = require('minimist')(process.argv.slice(2))
+const pify = require('pify')
 
 const db = require('./db')
 
 let settingsCache
 
+function loadFixture () {
+  const fixture = argv.fixture
+  const fixturePath = fixture => path.resolve(__dirname, '..', 'test', 'fixtures', fixture + '.json')
+
+  return fixture
+  ? pify(fs.readFile)(fixturePath(fixture)).then(JSON.parse)
+  : Promise.resolve({})
+}
+
+function isEquivalentField (a, b) {
+  return _.isEqual(
+    [a.fieldLocator.code, a.fieldLocator.fieldScope],
+    [b.fieldLocator.code, b.fieldLocator.fieldScope]
+  )
+}
+
+// b overrides a
+function mergeValues (a, b) {
+  return _.unionWith(isEquivalentField, b, a)
+}
+
 function load (versionId) {
   if (!versionId) throw new Error('versionId is required')
 
-  return Promise.all([loadConfig(versionId), loadAccounts()])
-  .then(([config, accounts]) => ({
-    config,
+  return Promise.all([loadConfig(versionId), loadAccounts(), loadFixture()])
+  .then(([config, accounts, fixture]) => ({
+    config: mergeValues(config, fixture),
     accounts
   }))
 }
@@ -67,5 +93,7 @@ module.exports = {
   loadConfig,
   load,
   loadLatest,
-  save
+  save,
+  loadFixture,
+  mergeValues
 }