Add failing test for updating token details

test/unit/preferences-controller-test.js

@@ -0,0 +1,48 @@
+const assert = require('assert')
+const PreferencesController = require('../../app/scripts/controllers/preferences')
+
+describe('preferences controller', function () {
+  let preferencesController
+
+  before(() => {
+    preferencesController = new PreferencesController()
+  })
+
+  describe('addToken', function () {
+    it('should add that token to its state', async function () {
+      const address = '0xabcdef1234567'
+      const symbol = 'ABBR'
+      const decimals = 5
+
+      await preferencesController.addToken(address, symbol, decimals)
+
+      const tokens = preferencesController.getTokens()
+      assert.equal(tokens.length, 1, 'one token added')
+
+      const added = tokens[0]
+      assert.equal(added.address, address, 'set address correctly')
+      assert.equal(added.symbol, symbol, 'set symbol correctly')
+      assert.equal(added.decimals, decimals, 'set decimals correctly')
+    })
+
+    it('should allow updating a token value', async function () {
+      const address = '0xabcdef1234567'
+      const symbol = 'ABBR'
+      const decimals = 5
+
+      await preferencesController.addToken(address, symbol, decimals)
+
+      const newDecimals = 6
+      await preferencesController.addToken(address, symbol, newDecimals)
+
+      const tokens = preferencesController.getTokens()
+      assert.equal(tokens.length, 1, 'one token added')
+
+      const added = tokens[0]
+      assert.equal(added.address, address, 'set address correctly')
+      assert.equal(added.symbol, symbol, 'set symbol correctly')
+      assert.equal(added.decimals, newDecimals, 'updated decimals correctly')
+    })
+  })
+})
+