Added EncryptDeployTokensTokens spec file

spec/migrations/encrypt_deploy_tokens_tokens_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+require Rails.root.join('db', 'post_migrate', '20190711201818_encrypt_deploy_tokens_tokens.rb')
+
+describe EncryptDeployTokensTokens, :migration do
+  let(:migration) { described_class.new }
+  let(:deployment_tokens) { table(:deploy_tokens) }
+  let(:plaintext) { "secret-token" }
+  let(:expires_at) { DateTime.now + 1.year }
+  let(:ciphertext) { Gitlab::CryptoHelper.aes256_gcm_encrypt(plaintext) }
+
+  describe '#up' do
+    it 'keeps plaintext token the same and populates token_encrypted if not present' do
+      deploy_token = deployment_tokens.create!(
+        name: 'test_token',
+        read_repository: true,
+        expires_at: expires_at,
+        username: 'gitlab-token-1',
+        token: plaintext
+      )
+
+      migration.up
+
+      expect(deploy_token.reload.token).to eq(plaintext)
+      expect(deploy_token.reload.token_encrypted).to eq(ciphertext)
+    end
+  end
+
+  describe '#down' do
+    it 'decrypts encrypted token and saves it' do
+      deploy_token = deployment_tokens.create!(
+        name: 'test_token',
+        read_repository: true,
+        expires_at: expires_at,
+        username: 'gitlab-token-1',
+        token_encrypted: ciphertext
+      )
+
+      migration.down
+
+      expect(deploy_token.reload.token).to eq(plaintext)
+      expect(deploy_token.reload.token_encrypted).to eq(ciphertext)
+    end
+  end
+end